15 Filter Effects

Contents

• 15.1 Introduction
• 15.2 An example
• 15.3 The 'filter' element
• 15.4 The 'filter' property
• 15.5 Filter effects region
• 15.6 Accessing the background image
• 15.7 Filter primitives overview
  • 15.7.1 Overview
  • 15.7.2 Common attributes
  • 15.7.3 Filter primitive subregion
• 15.8 Light source elements and properties
  • 15.8.1 Introduction
  • 15.8.2 Light source 'feDistantLight'
  • 15.8.3 Light source 'fePointLight'
  • 15.8.4 Light source 'feSpotLight'
  • 15.8.5 The 'lighting-color' property
• 15.9 Filter primitive 'feBlend'
• 15.10 Filter primitive 'feColorMatrix'
• 15.11 Filter primitive 'feComponentTransfer'
• 15.12 Filter primitive 'feComposite'
• 15.13 Filter primitive 'feConvolveMatrix'
• 15.14 Filter primitive 'feDiffuseLighting'
• 15.15 Filter primitive 'feDisplacementMap'
• 15.16 Filter primitive 'feFlood'
• 15.17 Filter primitive 'feGaussianBlur'
• 15.18 Filter primitive 'feImage'
• 15.19 Filter primitive 'feMerge'
• 15.20 Filter primitive 'feMorphology'
• 15.21 Filter primitive 'feOffset'
• 15.22 Filter primitive 'feSpecularLighting'
• 15.23 Filter primitive 'feTile'
• 15.24 Filter primitive 'feTurbulence'
• 15.25 Full Filter Module
• 15.26 Basic Filter Module
• 15.27 DOM interfaces

15.1 Introduction

This chapter describes SVG's declarative filter effects feature set, which when combined with the 2D power of SVG can describe much of the common artwork on the Web in such a way that client-side generation and alteration can be performed easily. In addition, the ability to apply filter effects to SVG graphics elements and container elements helps to maintain the semantic structure of the document, instead of resorting to images which aside from generally being a fixed resolution tend to obscure the original semantics of the elements they replace. This is especially true for effects applied to text.

A filter effect consists of a series of graphics operations that are applied to a given source graphic to produce a modified graphical result. The result of the filter effect is rendered to the target device instead of the original source graphic. The following illustrates the process:

View this example as SVG (SVG-enabled browsers only)
 

Filter effects are defined by 'filter' elements. To apply a filter effect to a graphics element or a container element, you set the value of the 'filter' property on the given element such that it references the filter effect.

Each 'filter' element contains a set of filter primitives as its children. Each filter primitive performs a single fundamental graphical operation (e.g., a blur or a lighting effect) on one or more inputs, producing a graphical result. Because most of the filter primitives represent some form of image processing, in most cases the output from a filter primitive is a single RGBA image.

The original source graphic or the result from a filter primitive can be used as input into one or more other filter primitives. A common application is to use the source graphic multiple times. For example, a simple filter could replace one graphic by two by adding a black copy of original source graphic offset to create a drop shadow. In effect, there are now two layers of graphics, both with the same original source graphics.

When applied to container elements such as 'g', the 'filter' property applies to the contents of the group as a whole. The group's children do not render to the screen directly; instead, the graphics commands necessary to render the children are stored temporarily. Typically, the graphics commands are executed as part of the processing of the referenced 'filter' element via use of the keywords SourceGraphic or SourceAlpha. Filter effects can be applied to container elements with no content (e.g., an empty 'g' element), in which case the SourceGraphic or SourceAlpha consist of a transparent black rectangle that is the size of the filter effects region.

Sometimes filter primitives result in undefined pixels. For example, filter primitive 'feOffset' can shift an image down and to the right, leaving undefined pixels at the top and left. In these cases, the undefined pixels are set to transparent black.

15.2 An example

The following shows an example of a filter effect.

Example filters01 - introducing filter effects.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
              "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="7.5cm" height="5cm" viewBox="0 0 200 120"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example filters01.svg - introducing filter effects</title>
  <desc>An example which combines multiple filter primitives
        to produce a 3D lighting effect on a graphic consisting
        of the string "SVG" sitting on top of oval filled in red
        and surrounded by an oval outlined in red.</desc>
  <defs>
    <filter id="MyFilter" filterUnits="userSpaceOnUse" x="0" y="0" width="200" height="120">
      <feGaussianBlur in="SourceAlpha" stdDeviation="4" result="blur"/>
      <feOffset in="blur" dx="4" dy="4" result="offsetBlur"/>
      <feSpecularLighting in="blur" surfaceScale="5" specularConstant=".75" 
                          specularExponent="20" lighting-color="#bbbbbb"  
                          result="specOut">
        <fePointLight x="-5000" y="-10000" z="20000"/>
      </feSpecularLighting>
      <feComposite in="specOut" in2="SourceAlpha" operator="in" result="specOut"/>
      <feComposite in="SourceGraphic" in2="specOut" operator="arithmetic" 
                   k1="0" k2="1" k3="1" k4="0" result="litPaint"/>
      <feMerge>
        <feMergeNode in="offsetBlur"/>
        <feMergeNode in="litPaint"/>
      </feMerge>
    </filter>
  </defs>
  <rect x="1" y="1" width="198" height="118" fill="#888888" stroke="blue" />
  <g filter="url(#MyFilter)" >
      <g>
      <path fill="none" stroke="#D90000" stroke-width="10" 
            d="M50,90 C0,90 0,30 50,30 L150,30 C200,30 200,90 150,90 z" />
      <path fill="#D90000" 
            d="M60,80 C30,80 30,40 60,40 L140,40 C170,40 170,80 140,80 z" />
      <g fill="#FFFFFF" stroke="black" font-size="45" font-family="Verdana" >
        <text x="52" y="76">SVG</text>
      </g>
    </g>
  </g>
</svg>

Example filters01

View this example as SVG (SVG-enabled browsers only)
 

The filter effect used in the example above is repeated here with reference numbers in the left column before each of the six filter primitives:

 
 
1
2
3
 
 
 
 
4
5
 
6
 
 
 

<filter id="MyFilter" filterUnits="userSpaceOnUse" x="0" y="0" width="200" height="120">
  <desc>Produces a 3D lighting effect.</desc>
  <feGaussianBlur in="SourceAlpha" stdDeviation="4" result="blur"/>
  <feOffset in="blur" dx="4" dy="4" result="offsetBlur"/>
  <feSpecularLighting in="blur" surfaceScale="5" specularConstant=".75" 
                      specularExponent="20" lighting-color="#bbbbbb" 
                      result="specOut">
    <fePointLight x="-5000" y="-10000" z="20000"/>
  </feSpecularLighting>
  <feComposite in="specOut" in2="SourceAlpha" operator="in" result="specOut"/>
  <feComposite in="SourceGraphic" in2="specOut" operator="arithmetic" 
               k1="0" k2="1" k3="1" k4="0" result="litPaint"/>
  <feMerge>
    <feMergeNode in="offsetBlur"/>
    <feMergeNode in="litPaint"/>
  </feMerge>
</filter>

The following pictures show the intermediate image results from each of the six filter elements:

1. Filter primitive 'feGaussianBlur' takes input SourceAlpha, which is the alpha channel of the source graphic. The result is stored in a temporary buffer named "blur". Note that "blur" is used as input to both filter primitives 2 and 3.
2. Filter primitive 'feOffset' takes buffer "blur", shifts the result in a positive direction in both x and y, and creates a new buffer named "offsetBlur". The effect is that of a drop shadow.
3. Filter primitive 'feSpecularLighting', uses buffer "blur" as a model of a surface elevation and generates a lighting effect from a single point source. The result is stored in buffer "specOut".
4. Filter primitive 'feComposite' masks out the result of filter primitive 3 by the original source graphics alpha channel so that the intermediate result is no bigger than the original source graphic.
5. Filter primitive 'feComposite' composites the result of the specular lighting with the original source graphic.
6. Filter primitive 'feMerge' composites two layers together. The lower layer consists of the drop shadow result from filter primitive 2. The upper layer consists of the specular lighting result from filter primitive 5.

15.3 The 'filter' element

The description of the 'filter' element follows:

<!ENTITY % filterExt "" >
<!ELEMENT filter (%descTitleMetadata;,(feBlend|feFlood|
  feColorMatrix|feComponentTransfer|
  feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|
  feGaussianBlur|feImage|feMerge|
  feMorphology|feOffset|feSpecularLighting|
  feTile|feTurbulence|
  animate|set
  %filterExt;)*) >
<!ATTLIST filter
  %stdAttrs;
  %xlinkRefAttrs;
  xlink:href %URI; #IMPLIED
  %langSpaceAttrs;
  externalResourcesRequired %Boolean; #IMPLIED
  class %ClassList; #IMPLIED
  style %StyleSheet; #IMPLIED
  %PresentationAttributes-All;
  filterUnits (userSpaceOnUse | objectBoundingBox) #IMPLIED
  primitiveUnits (userSpaceOnUse | objectBoundingBox) #IMPLIED
  x %Coordinate; #IMPLIED
  y %Coordinate; #IMPLIED
  width %Length; #IMPLIED
  height %Length; #IMPLIED
  filterRes %NumberOptionalNumber; #IMPLIED >

Properties inherit into the 'filter' element from its ancestors; properties do not inherit from the element referencing the 'filter' element.

'filter' elements are never rendered directly; their only usage is as something that can be referenced using the 'filter' property. The 'display' property does not apply to the 'filter' element; thus, 'filter' elements are not directly rendered even if the 'display' property is set to a value other than none, and 'filter' elements are available for referencing even when the 'display' property on the 'filter' element or any of its ancestors is set to none.

15.4 The 'filter' property

The description of the 'filter' property is as follows:

<uri>

A URI reference to a 'filter' element which defines the filter effects that shall be applied to this element.

none

Do not apply any filter effects to this element.

15.5 Filter effects region

A 'filter' element can define a region on the canvas to which a given filter effect applies and can provide a resolution for any intermediate continuous tone images used to process any raster-based filter primitives. The 'filter' element has the following attributes which work together to define the filter effects region:

• filterUnits={ userSpaceOnUse | objectBoundingBox }.
  Defines the coordinate system for attributes x, y, width, height.
  If filterUnits="userSpaceOnUse", x, y, width, height represent values in the current user coordinate system in place at the time when the 'filter' element is referenced (i.e., the user coordinate system for the element referencing the 'filter' element via a 'filter' property).
  If filterUnits="objectBoundingBox", then x, y, width, height represent fractions or percentages of the bounding box on the referencing element (see Object bounding box units).
  If attribute filterUnits is not specified, then the effect is as if a value of objectBoundingBox were specified.
  Animatable: yes.
• x, y, width, height, which define a rectangular region on the canvas to which this filter applies.
  The amount of memory and processing time required to apply the filter are related to the size of this rectangle and the filterRes attribute of the filter.
  The coordinate system for these attributes depends on the value for attribute filterUnits.
  Negative values for width or height are an error (see Error processing). Zero values disable rendering of the element which referenced the filter.
  The bounds of this rectangle act as a hard clipping region for each filter primitive included with a given 'filter' element; thus, if the effect of a given filter primitive would extend beyond the bounds of the rectangle (this sometimes happens when using a 'feGaussianBlur' filter primitive with a very large stdDeviation), parts of the effect will get clipped.
  If x or y is not specified, the effect is as if a value of "-10%" were specified.
  If width or height is not specified, the effect is as if a value of "120%" were specified.
  Animatable: yes.
• filterRes (which has the form x-pixels [y-pixels]) indicates the width and height of the intermediate images in pixels. If not provided, then a reasonable default resolution appropriate for the target device will be used. (For displays, an appropriate display resolution, preferably the current display's pixel resolution, is the default. For printing, an appropriate common printer resolution, such as 400dpi, is the default.)
  Care should be taken when assigning a non-default value to this attribute. Too small of a value may result in unwanted pixelation in the result. Too large of a value may result in slow processing and large memory usage.
  Negative values are an error (see Error processing). Zero values disable rendering of the element which referenced the filter.
  Animatable: yes.

Note that both of the two possible value for filterUnits (i.e., objectBoundingBox and userSpaceOnUse) result in a filter region whose coordinate system has its X-axis and Y-axis each parallel to the X-axis and Y-axis, respectively, of the user coordinate system for the element to which the filter will be applied.

Sometimes implementers can achieve faster performance when the filter region can be mapped directly to device pixels; thus, for best performance on display devices, it is suggested that authors define their region such that SVG user agent can align the filter region pixel-for-pixel with the background. In particular, for best filter effects performance, avoid rotating or skewing the user coordinate system. Explicit values for attribute filterRes can either help or harm performance. If filterRes is smaller than the automatic (i.e., default) filter resolution, then filter effect might have faster performance (usually at the expense of quality). If filterRes is larger than the automatic (i.e., default) filter resolution, then filter effects performance will usually be slower.

It is often necessary to provide padding space because the filter effect might impact bits slightly outside the tight-fitting bounding box on a given object. For these purposes, it is possible to provide negative percentage values for x, y and percentages values greater than 100% for width, height. This, for example, is why the defaults for the filter effects region are x="-10%" y="-10%" width="120%" height="120%".

15.6 Accessing the background image

Two possible pseudo input images for filter effects are BackgroundImage and BackgroundAlpha, which each represent an image snapshot of the canvas under the filter region at the time that the 'filter' element is invoked. BackgroundImage represents both the color values and alpha channel of the canvas (i.e., RGBA pixel values), whereas BackgroundAlpha represents only the alpha channel.

Implementations of SVG user agents often will need to maintain supplemental background image buffers in order to support the BackgroundImage and BackgroundAlpha pseudo input images. Sometimes, the background image buffers will contain an in-memory copy of the accumulated painting operations on the current canvas.

Because in-memory image buffers can take up significant system resources, SVG content must explicitly indicate to the SVG user agent that the document needs access to the background image before BackgroundImage and BackgroundAlpha pseudo input images can be used. The property which enables access to the background image is 'enable-background':

'enable-background' is only applicable to container elements and specifies how the SVG user agents manages the accumulation of the background image.

A value of new indicates two things:

• It enables the ability of children of the current container element to access the background image.
• It indicates that a new (i.e., initially transparent black) background image canvas is established and that (in effect) all children of the current container element shall be rendered into the new background image canvas in addition to being rendered onto the target device.

A meaning of enable-background: accumulate (the initial/default value) depends on context:

• If an ancestor container element has a property value of 'enable-background:new', then all graphics elements within the current container element are rendered both onto the parent container element's background image canvas and onto the target device.
• Otherwise, there is no current background image canvas, so it is only necessary to render graphics elements onto the target device. (No need to render to the background image canvas.)

If a filter effect specifies either the BackgroundImage or the BackgroundAlpha pseudo input images and no ancestor container element has a property value of 'enable-background:new', then the background image request is technically in error. Processing will proceed without interruption (i.e., no error message) and a transparent black image shall be provided in response to the request.

The optional <x>,<y>,<width>,<height> parameters on the new value indicate the subregion of the container element's user space where access to the background image is allowed to happen. These parameters enable the SVG user agent potentially to allocate smaller temporary image buffers than the default values, which might require the SVG user agent to allocate buffers as large as the current viewport. Thus, the values <x>,<y>,<width>,<height> act as a clipping rectangle on the background image canvas. Negative values for <width> or <height> are an error (see Error processing). If more than zero but less than four of the values <x>,<y>,<width> and <height> are specified or if zero values are specified for <width> or <height>, BackgroundImage and BackgroundAlpha are processed as if background image processing were not enabled.

Assume you have an element E in the document and that E has a series of ancestors A₁ (its immediate parent), A₂, etc. (Note: A₀ is E.) Each ancestor A_i will have a corresponding temporary background image offscreen buffer BUF_i. The contents of the background image available to a 'filter' referenced by E is defined as follows:

• Find the element A_i with the smallest subscript i (including A₀=E) for which the 'enable-background' property has the value new. (Note: if there is no such ancestor element, then there is no background image available to E, in which case a transparent black image will be used as E's background image.)
• For each A_i (from i=n to 1), initialize BUF_i to transparent black. Render all children of A_i up to but not including A_i-1 into BUF_i. The children are painted, then filtered, clipped, masked and composited using the various painting, filtering, clipping, masking and object opacity settings on the given child. Any filter effects, masking and group opacity that might be set on A_i do not apply when rendering the children of A_i into BUF_i.
  (Note that for the case of A₀=E, the graphical contents of E are not rendered into BUF₁ and thus are not part of the background image available to E. Instead, the graphical contents of E are available via the SourceGraphic and SourceAlpha pseudo input images.)
• Then, for each A_i (from i=1 to n-1), composite BUF_i into BUF_i+1.
• The accumulated result (i.e., BUF_n) represents the background image available to E.

Example enable-background-01 illustrates the rules for background image processing.

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
  "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="13.5cm" height="2.7cm" viewBox="0 0 1350 270"
     xmlns="http://www.w3.org/2000/svg" version="1.1">
  <title>Example enable-background01</title>
  <desc>This test case shows five pictures which illustrate the rules
        for background image processing.</desc>

  <defs>
    <filter id="ShiftBGAndBlur" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter discards the SourceGraphic, if any, and just produces
        a result consisting of the BackgroundImage shifted down 125 units
        and then blurred.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" />
    </filter>
    <filter id="ShiftBGAndBlur_WithSourceGraphic" 
            filterUnits="userSpaceOnUse" x="0" y="0" width="1200" height="400">
      <desc>
        This filter takes the BackgroundImage, shifts it down 125 units, blurs it,
        and then renders the SourceGraphic on top of the shifted/blurred background.
      </desc>
      <feOffset in="BackgroundImage" dx="0" dy="125" />
      <feGaussianBlur stdDeviation="8" result="blur" />
      <feMerge>
        <feMergeNode in="blur"/>
        <feMergeNode in="SourceGraphic"/>
      </feMerge>
    </filter>
  </defs>

  <g transform="translate(0,0)">
    <desc>The first picture is our reference graphic without filters.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(270,0)">
    <desc>The second adds an empty 'g' element which invokes ShiftBGAndBlur.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <g filter="url(#ShiftBGAndBlur)"/>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(540,0)">
    <desc>The third invokes ShiftBGAndBlur on the inner group.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g filter="url(#ShiftBGAndBlur)" opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(810,0)">
    <desc>The fourth invokes ShiftBGAndBlur on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>

  <g enable-background="new" transform="translate(1080,0)">
    <desc>The fifth invokes ShiftBGAndBlur_WithSourceGraphic on the triangle.</desc>
    <rect x="25" y="25" width="100" height="100" fill="red"/>
    <g opacity=".5">
      <circle cx="125" cy="75" r="45" fill="green"/>
      <polygon points="160,25 160,125 240,75" fill="blue"
               filter="url(#ShiftBGAndBlur_WithSourceGraphic)"/>
    </g>
    <rect x="5" y="5" width="260" height="260" fill="none" stroke="blue"/>
  </g>
</svg>

Example enable-background-01

View this example as SVG (SVG-enabled browsers only)
 

The example above contains five parts, described as follows:

1. The first set is the reference graphic. The reference graphic consists of a red rectangle followed by a 50% transparent 'g' element. Inside the 'g' is a green circle that partially overlaps the rectangle and a a blue triangle that partially overlaps the circle. The three objects are then outlined by a rectangle stroked with a thin blue line. No filters are applied to the reference graphic.
2. The second set enables background image processing and adds an empty 'g' element which invokes the ShiftBGAndBlur filter. This filter takes the current accumulated background image (i.e., the entire reference graphic) as input, shifts its offscreen down, blurs it, and then writes the result to the canvas. Note that the offscreen for the filter is initialized to transparent black, which allows the already rendered rectangle, circle and triangle to show through after the filter renders its own result to the canvas.
3. The third set enables background image processing and instead invokes the ShiftBGAndBlur filter on the inner 'g' element. The accumulated background at the time the filter is applied contains only the red rectangle. Because the children of the inner 'g' (i.e., the circle and triangle) are not part of the inner 'g' element's background and because ShiftBGAndBlur ignores SourceGraphic, the children of the inner 'g' do not appear in the result.
4. The fourth set enables background image processing and invokes the ShiftBGAndBlur on the 'polygon' element that draws the triangle. The accumulated background at the time the filter is applied contains the red rectangle plus the green circle ignoring the effect of the 'opacity' property on the inner 'g' element. (Note that the blurred green circle at the bottom does not let the red rectangle show through on its left side. This is due to ignoring the effect of the 'opacity' property.) Because the triangle itself is not part of the accumulated background and because ShiftBGAndBlur ignores SourceGraphic, the triangle does not appear in the result.
5. The fifth set is the same as the fourth except that filter ShiftBGAndBlur_WithSourceGraphic is invoked instead of ShiftBGAndBlur. ShiftBGAndBlur_WithSourceGraphic performs the same effect as ShiftBGAndBlur, but then renders the SourceGraphic on top of the shifted, blurred background image. In this case, SourceGraphic is the blue triangle; thus, the result is the same as in the fourth case except that the blue triangle now appears.

15.7 Filter primitives overview

15.7.1 Overview

This section describes the various filter primtives that can be assembled to achieve a particular filter effect.

Unless otherwise stated, all image filters operate on premultiplied RGBA samples. Filters which work more naturally on non-premultiplied data (feColorMatrix and feComponentTransfer) will temporarily undo and redo premultiplication as specified. All raster effect filtering operations take 1 to N input RGBA images, additional attributes as parameters, and produce a single output RGBA image.

The RGBA result from each filter primitive will be clamped into the allowable ranges for colors and opacity values. Thus, for example, the result from a given filter primitive will have any negative color values or opacity values adjusted up to color/opacity of zero.

The color space in which a particular filter primitive performs its operations is determined by the value of property 'color-interpolation-filters' on the given filter primitive. A different property, 'color-interpolation' determines the color space for other color operations. Because these two properties have different initial values ('color-interpolation-filters' has an initial value of linearRGB whereas 'color-interpolation' has an initial value of sRGB), in some cases to achieve certain results (e.g., when coordinating gradient interpolation with a filtering operation) it will be necessary to explicitly set 'color-interpolation' to linearRGB or 'color-interpolation-filters' to sRGB on particular elements. Note that the examples below do not explicitly set either 'color-interpolation' or 'color-interpolation-filters', so the initial values for these properties apply to the examples.

15.7.2 Common attributes

The following attributes are available for most of the filter primitives:

<!ENTITY % filter_primitive_attributes
  "x %Coordinate; #IMPLIED
   y %Coordinate; #IMPLIED
   width %Length; #IMPLIED
   height %Length; #IMPLIED
   result CDATA #IMPLIED" >

<!ENTITY % filter_primitive_attributes_with_in
  "%filter_primitive_attributes;
   in CDATA #IMPLIED">

15.7.3 Filter primitive subregion

All filter primitives have attributes x, y, width and height which identify a subregion which restricts calculation and rendering of the given filter primitive. These attributes are defined according to the same rules as other filter primitives' coordinate and length attributes and thus represent values in the coordinate system established by attribute primitiveUnits on the 'filter' element.

x, y, width and height default to the union (i.e., tightest fitting bounding box) of the subregions defined for all referenced nodes. If there are no referenced nodes (e.g., for 'feImage' or 'feTurbulence'), or one or more of the referenced nodes is a standard input (one of SourceGraphic, SourceAlpha, BackgroundImage, BackgroundAlpha, FillPaint or StrokePaint), or for 'feTile' (which is special because its principal function is to replicate the referenced node in X and Y and thereby produce a usually larger result), the default subregion is 0%,0%,100%,100%, where percentages are relative to the dimensions of the filter region.

x, y, width and height act as a hard clip clipping rectangle.

All intermediate offscreens are defined to not exceed the intersection of x, y, width and height with the filter region. The filter region and any of the x, y, width and height subregions are to be set up such that all offscreens are made big enough to accommodate any pixels which even partly intersect with either the filter region or the x,y,width,height subregions.

'feTile' references a previous filter primitive and then stitches the tiles together based on the x, y, width and height values of the referenced filter primitive in order to fill its own filter primitive subregion.

15.8 Light source elements and properties

15.8.1 Introduction

The following sections define the elements that define a light source, 'feDistantLight', 'fePointLight' and 'feSpotLight', and property 'lighting-color', which defines the color of the light.

15.8.2 Light source 'feDistantLight'

<!ELEMENT feDistantLight (animate|set)* >
<!ATTLIST feDistantLight
  %stdAttrs;
  azimuth %Number; #IMPLIED
  elevation %Number; #IMPLIED >

15.8.3 Light source 'fePointLight'

<!ELEMENT fePointLight (animate|set)* >
<!ATTLIST fePointLight
  %stdAttrs;
  x %Number; #IMPLIED
  y %Number; #IMPLIED
  z %Number; #IMPLIED >

15.8.4 Light source 'feSpotLight'

<!ELEMENT feSpotLight (animate|set)* >
<!ATTLIST feSpotLight
  %stdAttrs;
  x %Number; #IMPLIED
  y %Number; #IMPLIED
  z %Number; #IMPLIED
  pointsAtX %Number; #IMPLIED
  pointsAtY %Number; #IMPLIED
  pointsAtZ %Number; #IMPLIED
  specularExponent %Number; #IMPLIED
  limitingConeAngle %Number; #IMPLIED >

15.8.5 The 'lighting-color' property

The 'lighting-color' property defines the color of the light source for filter primitives 'feDiffuseLighting' and 'feSpecularLighting'.

15.9 Filter primitive 'feBlend'

This filter composites two objects together using commonly used imaging software blending modes. It performs a pixel-wise combination of two input images.

<!ELEMENT feBlend (animate|set)* >
<!ATTLIST feBlend
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  in2 CDATA #REQUIRED
  mode (normal | multiply | screen | darken | lighten) "normal" >

For all feBlend modes, the result opacity is computed as follows:

qr = 1 - (1-qa)*(1-qb)

For the compositing formulas below, the following definitions apply:

cr = Result color (RGB) - premultiplied 
qa = Opacity value at a given pixel for image A 
qb = Opacity value at a given pixel for image B 
ca = Color (RGB) at a given pixel for image A - premultiplied 
cb = Color (RGB) at a given pixel for image B - premultiplied 

The following table provides the list of available image blending modes:

'normal' blend mode is equivalent to operator="over" on the 'feComposite' filter primitive, matches the blending method used by 'feMerge' and matches the simple alpha compositing technique used in SVG for all compositing outside of filter effects.

Example feBlend shows examples of the five blend modes.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="5cm" height="5cm" viewBox="0 0 500 500" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <title>Example feBlend - Examples of feBlend modes</title>
  <desc>Five text strings blended into a gradient,
        with one text string for each of the five feBlend modes.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="300" y2="0">
      <stop offset="0" stop-color="#000000" />
      <stop offset=".33" stop-color="#ffffff" />
      <stop offset=".67" stop-color="#ff0000" />
      <stop offset="1" stop-color="#808080" />
    </linearGradient>
    <filter id="Normal">
      <feBlend mode="normal" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Multiply">
      <feBlend mode="multiply" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Screen">
      <feBlend mode="screen" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Darken">
      <feBlend mode="darken" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
    <filter id="Lighten">
      <feBlend mode="lighten" in2="BackgroundImage" in="SourceGraphic"/>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="498" height="498"/>
  <g enable-background="new" >
    <rect x="100" y="20" width="300" height="460" fill="url(#MyGradient)" />
    <g font-family="Verdana" font-size="75" fill="#888888" fill-opacity=".6" >
      <text x="50" y="90" filter="url(#Normal)" >Normal</text>
      <text x="50" y="180" filter="url(#Multiply)" >Multiply</text>
      <text x="50" y="270" filter="url(#Screen)" >Screen</text>
      <text x="50" y="360" filter="url(#Darken)" >Darken</text>
      <text x="50" y="450" filter="url(#Lighten)" >Lighten</text>
    </g>
  </g>
</svg>

Example feBlend

View this example as SVG (SVG-enabled browsers only)
 

15.10 Filter primitive 'feColorMatrix'

This filter applies a matrix transformation:

| R' |     | a00 a01 a02 a03 a04 |   | R |

| G' |     | a10 a11 a12 a13 a14 |   | G |

| B' |  =  | a20 a21 a22 a23 a24 | * | B |

| A' |     | a30 a31 a32 a33 a34 |   | A |

| 1  |     |  0   0   0   0   1  |   | 1 |

on the RGBA color and alpha values of every pixel on the input graphics to produce a result with a new set of RGBA color and alpha values.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation.

These matrices often perform an identity mapping in the alpha channel. If that is the case, an implementation can avoid the costly undoing and redoing of the premultiplication for all pixels with A = 1.

<!ELEMENT feColorMatrix (animate|set)* >
<!ATTLIST feColorMatrix
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  type (matrix | saturate | hueRotate | luminanceToAlpha) "matrix"
  values CDATA #IMPLIED >

Example feColorMatrix shows examples of the four types of feColorMatrix operations.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="8cm" height="5cm" viewBox="0 0 800 500" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <title>Example feColorMatrix - Examples of feColorMatrix operations</title>
  <desc>Five text strings showing the effects of feColorMatrix: 
        an unfiltered text string acting as a reference, 
        use of the feColorMatrix matrix option to convert to grayscale,
        use of the feColorMatrix saturate option,
        use of the feColorMatrix hueRotate option,
        and use of the feColorMatrix luminanceToAlpha option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="500" y2="0">
      <stop offset="0" stop-color="#ff00ff" />
      <stop offset=".33" stop-color="#88ff88" />
      <stop offset=".67" stop-color="#2020ff" />
      <stop offset="1" stop-color="#d00000" />
    </linearGradient>
    <filter id="Matrix" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="matrix" in="SourceGraphic"
           values=".33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0 
                   .33 .33 .33 0 0"/>
    </filter>
    <filter id="Saturate40" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="saturate" in="SourceGraphic" values="40%"/>
    </filter>
    <filter id="HueRotate90" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="hueRotate" in="SourceGraphic" values="90"/>
    </filter>
    <filter id="LuminanceToAlpha" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feColorMatrix type="luminanceToAlpha" in="SourceGraphic" result="a"/>
      <feComposite in="SourceGraphic" in2="a" operator="in" />
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="498"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="500" height="20" />
    <text x="100" y="90">Unfiltered</text>
    <text x="100" y="190" filter="url(#Matrix)" >Matrix</text>
    <text x="100" y="290" filter="url(#Saturate40)" >Saturate</text>
    <text x="100" y="390" filter="url(#HueRotate90)" >HueRotate</text>
    <text x="100" y="490" filter="url(#LuminanceToAlpha)" >Luminance</text>
  </g>
</svg>

Example feColorMatrix

View this example as SVG (SVG-enabled browsers only)
 

15.11 Filter primitive 'feComponentTransfer'

This filter primitive performs component-wise remapping of data as follows:

R' = feFuncR( R )
G' = feFuncG( G )
B' = feFuncB( B )
A' = feFuncA( A )

for every pixel. It allows operations like brightness adjustment, contrast adjustment, color balance or thresholding.

The calculations are performed on non-premultiplied color values. If the input graphics consists of premultiplied color values, those values are automatically converted into non-premultiplied color values for this operation. (Note that the undoing and redoing of the premultiplication can be avoided if feFuncA is the identity transform and all alpha values on the source graphic are set to 1.)

<!ELEMENT feComponentTransfer (feFuncR?,feFuncG?,feFuncB?,feFuncA?) >
<!ATTLIST feComponentTransfer
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in; >

<!ENTITY % component_transfer_function_attributes
  "type (identity | table | discrete | linear | gamma) #REQUIRED
   tableValues CDATA #IMPLIED
   slope %Number; #IMPLIED
   intercept %Number; #IMPLIED
   amplitude %Number; #IMPLIED
   exponent %Number; #IMPLIED
   offset %Number; #IMPLIED" >

<!ELEMENT feFuncR (animate|set)* >
<!ATTLIST feFuncR
  %stdAttrs;
  %component_transfer_function_attributes; >

<!ELEMENT feFuncG (animate|set)* >
<!ATTLIST feFuncG
  %stdAttrs;
  %component_transfer_function_attributes; >

<!ELEMENT feFuncB (animate|set)* >
<!ATTLIST feFuncB
  %stdAttrs;
  %component_transfer_function_attributes; >

<!ELEMENT feFuncA (animate|set)* >
<!ATTLIST feFuncA
  %stdAttrs;
  %component_transfer_function_attributes; >

The specification of the transfer functions is defined by the sub-elements to 'feComponentTransfer':

'feFuncR', transfer function for red component of the input graphic

'feFuncG', transfer function for green component of the input graphic

'feFuncB', transfer function for blue component of the input graphic

'feFuncA', transfer function for alpha component of the input graphic

The attributes below apply to sub-elements 'feFuncR', 'feFuncG', 'feFuncB' and 'feFuncA' define the transfer functions.

Example feComponentTransfer shows examples of the four types of feComponentTransfer operations.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="8cm" height="4cm" viewBox="0 0 800 400" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <title>Example feComponentTransfer - Examples of feComponentTransfer operations</title>
  <desc>Four text strings showing the effects of feComponentTransfer: 
        an identity function acting as a reference, 
        use of the feComponentTransfer table option,
        use of the feComponentTransfer linear option,
        and use of the feComponentTransfer gamma option.</desc>
  <defs>
    <linearGradient id="MyGradient" gradientUnits="userSpaceOnUse"
            x1="100" y1="0" x2="600" y2="0">
      <stop offset="0" stop-color="#ff0000" />
      <stop offset=".33" stop-color="#00ff00" />
      <stop offset=".67" stop-color="#0000ff" />
      <stop offset="1" stop-color="#000000" />
    </linearGradient>
    <filter id="Identity" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="identity"/>
        <feFuncG type="identity"/>
        <feFuncB type="identity"/>
        <feFuncA type="identity"/>
      </feComponentTransfer>
    </filter>
    <filter id="Table" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="table" tableValues="0 0 1 1"/>
        <feFuncG type="table" tableValues="1 1 0 0"/>
        <feFuncB type="table" tableValues="0 1 1 0"/>
      </feComponentTransfer>
    </filter>
    <filter id="Linear" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="linear" slope=".5" intercept=".25"/>
        <feFuncG type="linear" slope=".5" intercept="0"/>
        <feFuncB type="linear" slope=".5" intercept=".5"/>
      </feComponentTransfer>
    </filter>
    <filter id="Gamma" filterUnits="objectBoundingBox" 
            x="0%" y="0%" width="100%" height="100%">
      <feComponentTransfer>
        <feFuncR type="gamma" amplitude="2" exponent="5" offset="0"/>
        <feFuncG type="gamma" amplitude="2" exponent="3" offset="0"/>
        <feFuncB type="gamma" amplitude="2" exponent="1" offset="0"/>
      </feComponentTransfer>
    </filter>
  </defs>
  <rect fill="none" stroke="blue"  
        x="1" y="1" width="798" height="398"/>
  <g font-family="Verdana" font-size="75" 
            font-weight="bold" fill="url(#MyGradient)" >
    <rect x="100" y="0" width="600" height="20" />
    <text x="100" y="90">Identity</text>
    <text x="100" y="190" filter="url(#Table)" >TableLookup</text>
    <text x="100" y="290" filter="url(#Linear)" >LinearFunc</text>
    <text x="100" y="390" filter="url(#Gamma)" >GammaFunc</text>
  </g>
</svg>

Example feComponentTransfer

View this example as SVG (SVG-enabled browsers only)
 

15.12 Filter primitive 'feComposite'

This filter performs the combination of the two input images pixel-wise in image space using one of the Porter-Duff [PORTERDUFF] compositing operations: over, in, atop, out, xor. Additionally, a component-wise arithmetic operation (with the result clamped between [0..1]) can be applied.

The arithmetic operation is useful for combining the output from the 'feDiffuseLighting' and 'feSpecularLighting' filters with texture data. It is also useful for implementing dissolve. If the arithmetic operation is chosen, each result pixel is computed using the following formula:

result = k1*i1*i2 + k2*i1 + k3*i2 + k4

For this filter primitive, the extent of the resulting image might grow as described in the section that describes the filter primitive subregion.

<!ELEMENT feComposite (animate|set)* >
<!ATTLIST feComposite
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  in2 CDATA #REQUIRED
  operator (over | in | out | atop | xor | arithmetic) "over"
  k1 %Number; #IMPLIED
  k2 %Number; #IMPLIED
  k3 %Number; #IMPLIED
  k4 %Number; #IMPLIED >

Example feComposite shows examples of the six types of feComposite operations. It also shows two different techniques to using the BackgroundImage as part of the compositing operation.

The first two rows render bluish triangles into the background. A filter is applied which composites reddish triangles into the bluish triangles using one of the compositing operations. The result from compositing is drawn onto an opaque white temporary surface, and then that result is written to the canvas. (The opaque white temporary surface obliterates the original bluish triangle.)

The last two rows apply the same compositing operations of reddish triangles into bluish triangles. However, the compositing result is directly blended into the canvas (the opaque white temporary surface technique is not used). In some cases, the results are different than when a temporary opaque white surface is used. The original bluish triangle from the background shines through wherever the compositing operation results in completely transparent pixel. In other cases, the result from compositing is blended into the bluish triangle, resulting in a different final color value.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="330" height="195" viewBox="0 0 1100 650" version="1.1"
     xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>Example feComposite - Examples of feComposite operations</title>
  <desc>Four rows of six pairs of overlapping triangles depicting
        the six different feComposite operators under different
        opacity values and different clearing of the background.</desc>
    <defs>
    <desc>Define two sets of six filters for each of the six compositing operators.
          The first set wipes out the background image by flooding with opaque white.
          The second set does not wipe out the background, with the result
          that the background sometimes shines through and is other cases
          is blended into itself (i.e., "double-counting").</desc>
    <filter id="overFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="inFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="outFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="atopFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="xorFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="arithmeticFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feFlood flood-color="#ffffff" flood-opacity="1" result="flood"/>
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
      <feMerge> <feMergeNode in="flood"/> <feMergeNode in="comp"/> </feMerge>
    </filter>
    <filter id="overNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="over" result="comp"/>
    </filter>
    <filter id="inNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="in" result="comp"/>
    </filter>
    <filter id="outNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="out" result="comp"/>
    </filter>
    <filter id="atopNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="atop" result="comp"/>
    </filter>
    <filter id="xorNoFlood" filterUnits="objectBoundingBox" x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" operator="xor" result="comp"/>
    </filter>
    <filter id="arithmeticNoFlood" filterUnits="objectBoundingBox" 
            x="-5%" y="-5%" width="110%" height="110%">
      <feComposite in="SourceGraphic" in2="BackgroundImage" result="comp"
                   operator="arithmetic" k1=".5" k2=".5" k3=".5" k4=".5"/>
    </filter>
    <path id="Blue100" d="M 0 0 L 100 0 L 100 100 z" fill="#00ffff" />
    <path id="Red100" d="M 0 0 L 0 100 L 100 0 z" fill="#ff00ff" />
    <path id="Blue50" d="M 0 125 L 100 125 L 100 225 z" fill="#00ffff" fill-opacity=".5" />
    <path id="Red50" d="M 0 125 L 0 225 L 100 125 z" fill="#ff00ff" fill-opacity=".5" />
    <g id="TwoBlueTriangles">
      <use xlink:href="#Blue100"/>
      <use xlink:href="#Blue50"/>
    </g>
    <g id="BlueTriangles">
      <use transform="translate(275,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(400,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(525,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(650,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(775,25)" xlink:href="#TwoBlueTriangles"/>
      <use transform="translate(900,25)" xlink:href="#TwoBlueTriangles"/>
    </g>
  </defs>

  <rect fill="none" stroke="blue" x="1" y="1" width="1098" height="648"/>
  <g font-family="Verdana" font-size="40" shape-rendering="crispEdges">
    <desc>Render the examples using the filters that draw on top of
          an opaque white surface, thus obliterating the background.</desc>
    <g enable-background="new">
      <text x="15" y="75">opacity 1.0</text>
      <text x="15" y="115" font-size="27">(with feFlood)</text>
      <text x="15" y="200">opacity 0.5</text>
      <text x="15" y="240" font-size="27">(with feFlood)</text>
      <use xlink:href="#BlueTriangles"/>
      <g transform="translate(275,25)">
        <use xlink:href="#Red100" filter="url(#overFlood)" />
        <use xlink:href="#Red50" filter="url(#overFlood)" />
        <text x="5" y="275">over</text>
      </g>
      <g transform="translate(400,25)">
        <use xlink:href="#Red100" filter="url(#inFlood)" />
        <use xlink:href="#Red50" filter="url(#inFlood)" />
        <text x="35" y="275">in</text>
      </g>
      <g transform="translate(525,25)">
        <use xlink:href="#Red100" filter="url(#outFlood)" />
        <use xlink:href="#Red50" filter="url(#outFlood)" />
        <text x="15" y="275">out</text>
      </g>
      <g transform="translate(650,25)">
        <use xlink:href="#Red100" filter="url(#atopFlood)" />
        <use xlink:href="#Red50" filter="url(#atopFlood)" />
        <text x="10" y="275">atop</text>
      </g>
      <g transform="translate(775,25)">
        <use xlink:href="#Red100" filter="url(#xorFlood)" />
        <use xlink:href="#Red50" filter="url(#xorFlood)" />
        <text x="15" y="275">xor</text>
      </g>
      <g transform="translate(900,25)">
        <use xlink:href="#Red100" filter="url(#arithmeticFlood)" />
        <use xlink:href="#Red50" filter="url(#arithmeticFlood)" />
        <text x="-25" y="275">arithmetic</text>
      </g>
    </g>
    <g transform="translate(0,325)" enable-background="new">
    <desc>Render the examples using the filters that do not obliterate
          the background, thus sometimes causing the background to continue
          to appear in some cases, and in other cases the background
          image blends into itself ("double-counting").</desc>
      <text x="15" y="75">opacity 1.0</text>
      <text x="15" y="115" font-size="27">(without feFlood)</text>
      <text x="15" y="200">opacity 0.5</text>
      <text x="15" y="240" font-size="27">(without feFlood)</text>
      <use xlink:href="#BlueTriangles"/>
      <g transform="translate(275,25)">
        <use xlink:href="#Red100" filter="url(#overNoFlood)" />
        <use xlink:href="#Red50" filter="url(#overNoFlood)" />
        <text x="5" y="275">over</text>
      </g>
      <g transform="translate(400,25)">
        <use xlink:href="#Red100" filter="url(#inNoFlood)" />
        <use xlink:href="#Red50" filter="url(#inNoFlood)" />
        <text x="35" y="275">in</text>
      </g>
      <g transform="translate(525,25)">
        <use xlink:href="#Red100" filter="url(#outNoFlood)" />
        <use xlink:href="#Red50" filter="url(#outNoFlood)" />
        <text x="15" y="275">out</text>
      </g>
      <g transform="translate(650,25)">
        <use xlink:href="#Red100" filter="url(#atopNoFlood)" />
        <use xlink:href="#Red50" filter="url(#atopNoFlood)" />
        <text x="10" y="275">atop</text>
      </g>
      <g transform="translate(775,25)">
        <use xlink:href="#Red100" filter="url(#xorNoFlood)" />
        <use xlink:href="#Red50" filter="url(#xorNoFlood)" />
        <text x="15" y="275">xor</text>
      </g>
      <g transform="translate(900,25)">
        <use xlink:href="#Red100" filter="url(#arithmeticNoFlood)" />
        <use xlink:href="#Red50" filter="url(#arithmeticNoFlood)" />
        <text x="-25" y="275">arithmetic</text>
      </g>
    </g>
  </g>
</svg>

Example feComposite

View this example as SVG (SVG-enabled browsers only)
 

15.13 Filter primitive 'feConvolveMatrix'

feConvolveMatrix applies a matrix convolution filter effect. A convolution combines pixels in the input image with neighboring pixels to produce a resulting image. A wide variety of imaging operations can be achieved through convolutions, including blurring, edge detection, sharpening, embossing and beveling.

A matrix convolution is based on an n-by-m matrix (the convolution kernel) which describes how a given pixel value in the input image is combined with its neighboring pixel values to produce a resulting pixel value. Each result pixel is determined by applying the kernel matrix to the corresponding source pixel and its neighboring pixels. The basic convolution formula which is applied to each color value for a given pixel is:

RESULT_X,Y = ( 
              SUM _{I=0 to [orderY-1]} { 
                SUM _{J=0 to [orderX-1]} { 
                  SOURCE _{X-targetX+J, Y-targetY+I} *  kernelMatrix_{orderX-J-1,  orderY-I-1} 
                } 
              } 
            ) /  divisor +  bias

where "orderX" and "orderY" represent the X and Y values for the order attribute, "targetX" represents the value of the targetX attribute, "targetY" represents the value of the targetY attribute, "kernelMatrix" represents the value of the kernelMatrix attribute, "divisor" represents the value of the divisor attribute, and "bias" represents the value of the bias attribute.

Note in the above formulas that the values in the kernel matrix are applied such that the kernel matrix is rotated 180 degrees relative to the source and destination images in order to match convolution theory as described in many computer graphics textbooks.

To illustrate, suppose you have a input image which is 5 pixels by 5 pixels, whose color values for one of the color channels are as follows:

    0  20  40 235 235
  100 120 140 235 235
  200 220 240 235 235
  225 225 255 255 255
  225 225 255 255 255

and you define a 3-by-3 convolution kernel as follows:

  1 2 3
  4 5 6
  7 8 9

Let's focus on the color value at the second row and second column of the image (source pixel value is 120). Assuming the simplest case (where the input image's pixel grid aligns perfectly with the kernel's pixel grid) and assuming default values for attributes divisor, targetX and targetY, then resulting color value will be:

(9*  0 + 8* 20 + 7* 40 +
6*100 + 5*120 + 4*140 +
3*200 + 2*220 + 1*240) / (9+8+7+6+5+4+3+2+1)

Because they operate on pixels, matrix convolutions are inherently resolution-dependent. To make 'feConvolveMatrix produce resolution-independent results, an explicit value should be provided for either the filterRes attribute on the 'filter' element and/or attribute kernelUnitLength.

kernelUnitLength, in combination with the other attributes, defines an implicit pixel grid in the filter effects coordinate system (i.e., the coordinate system established by the primitiveUnits attribute). If the pixel grid established by kernelUnitLength is not scaled to match the pixel grid established by attribute filterRes (implicitly or explicitly), then the input image will be temporarily rescaled to match its pixels with kernelUnitLength. The convolution happens on the resampled image. After applying the convolution, the image is resampled back to the original resolution.

When the image must be resampled to match the coordinate system defined by kernelUnitLength prior to convolution, or resampled to match the device coordinate system after convolution, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the 'image-rendering' property setting. Note that implementations might choose approaches that minimize or eliminate resampling when not necessary to produce proper results, such as when the document is zoomed out such that kernelUnitLength is considerably smaller than a device pixel.

<!ELEMENT feConvolveMatrix (animate|set)* >
<!ATTLIST feConvolveMatrix
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  order %NumberOptionalNumber; #REQUIRED
  kernelMatrix CDATA #REQUIRED
  divisor %Number; #IMPLIED
  bias %Number; #IMPLIED
  targetX %Integer; #IMPLIED
  targetY %Integer; #IMPLIED
  edgeMode (duplicate|wrap|none) "duplicate" 
  kernelUnitLength %NumberOptionalNumber; #IMPLIED 
  preserveAlpha %Boolean; #IMPLIED >

15.14 Filter primitive 'feDiffuseLighting'

This filter primitive lights an image using the alpha channel as a bump map. The resulting image is an RGBA opaque image based on the light color with alpha = 1.0 everywhere. The lighting calculation follows the standard diffuse component of the Phong lighting model. The resulting image depends on the light color, light position and surface geometry of the input bump map.

The light map produced by this filter primitive can be combined with a texture image using the multiply term of the arithmetic 'feComposite' compositing method. Multiple light sources can be simulated by adding several of these light maps together before applying it to the texture image.

The formulas below make use of 3x3 filters. Because they operate on pixels, such filters are inherently resolution-dependent. To make 'feDiffuseLighting' produce resolution-independent results, an explicit value should be provided for either the filterRes attribute on the 'filter' element and/or attribute kernelUnitLength.

kernelUnitLength, in combination with the other attributes, defines an implicit pixel grid in the filter effects coordinate system (i.e., the coordinate system established by the primitiveUnits attribute). If the pixel grid established by kernelUnitLength is not scaled to match the pixel grid established by attribute filterRes (implicitly or explicitly), then the input image will be temporarily rescaled to match its pixels with kernelUnitLength. The 3x3 filters are applied to the resampled image. After applying the filter, the image is resampled back to its original resolution.

When the image must be resampled, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the 'image-rendering' property setting. Note that implementations might choose approaches that minimize or eliminate resampling when not necessary to produce proper results, such as when the document is zoomed out such that kernelUnitLength is considerably smaller than a device pixel.

For the formulas that follow, the Norm(Ax,Ay,Az) function is defined as:

Norm(A_x,A_y,A_z) = sqrt(A_x^2+A_y^2+A_z^2)

The resulting RGBA image is computed as follows:

D_r = k_d * N.L * L_r
D_g = k_d * N.L * L_g
D_b = k_d * N.L * L_b
D_a = 1.0

where

k_d = diffuse lighting constant
N = surface normal unit vector, a function of x and y
L = unit vector pointing from surface to light, a function of x and y in the point and spot light cases
L_r,L_g,L_b = RGB components of light, a function of x and y in the spot light case

N is a function of x and y and depends on the surface gradient as follows:

The surface described by the input alpha image A_in (x,y) is:

Z (x,y) = surfaceScale * A_in (x,y)

Surface normal is calculated using the Sobel gradient 3x3 filter. Different filter kernels are used depending on whether the given pixel is on the interior or an edge. For each case, the formula is:

N_x (x,y)= - surfaceScale * FACTOR_x *
           (K _x(0,0)*I(x-dx,y-dy) + K_x(1,0)*I(x,y-dy) + K_x(2,0)*I(x+dx,y-dy) +
            K _x(0,1)*I(x-dx,y)   + K_x(1,1)*I(x,y)   + K_x(2,1)*I(x+dx,y)   +
            K _x(0,2)*I(x-dx,y+dy) + K_x(1,2)*I(x,y+dy) + K_x(2,2)*I(x+dx,y+dy))
N_y (x,y)= - surfaceScale * FACTOR_y *
           (K _y(0,0)*I(x-dx,y-dy) + K_y(1,0)*I(x,y-dy) + K_y(2,0)*I(x+dx,y-dy) +
            K _y(0,1)*I(x-dx,y)   + K_y(1,1)*I(x,y)   + K_y(2,1)*I(x+dx,y)   +
            K _y(0,2)*I(x-dx,y+dy) + K_y(1,2)*I(x,y+dy) + K_y(2,2)*I(x+dx,y+dy))
N_z (x,y) = 1.0

N = (N_x, N_y, N_z) / Norm((N_x,N_y,N_z))

In these formulas, the dx and dy values (e.g., I(x-dx,y-dy)), represent deltas relative to a given (x,y) position for the purpose of estimating the slope of the surface at that point. These deltas are determined by the value (explicit or implicit) of attribute kernelUnitLength.

L, the unit vector from the image sample to the light, is calculated as follows:

For Infinite light sources it is constant:

L_x = cos(azimuth)*cos(elevation)
L_y = sin(azimuth)*cos(elevation)
L_z = sin(elevation)

For Point and spot lights it is a function of position:

L_x = Light_x - x
L_y = Light_y - y
L_z = Light_z - Z(x,y)

L = (L_x, L_y, L_z) / Norm(L_x, L_y, L_z)

where Light_x, Light_y, and Light_z are the input light position.

L_r,L_g,L_b, the light color vector, is a function of position in the spot light case only:

L_r = Light_r*pow((-L.S),specularExponent)
L_g = Light_g*pow((-L.S),specularExponent)
L_b = Light_b*pow((-L.S),specularExponent)

where S is the unit vector pointing from the light to the point (pointsAtX, pointsAtY, pointsAtZ) in the x-y plane:

S_x = pointsAtX - Light_x
S_y = pointsAtY - Light_y
S_z = pointsAtZ - Light_z

S = (S_x, S_y, S_z) / Norm(S_x, S_y, S_z)

If L.S is positive, no light is present. (L_r = L_g = L_b = 0)

<!ELEMENT feDiffuseLighting ((feDistantLight|fePointLight|feSpotLight),(animate|set|animateColor)*) >
<!ATTLIST feDiffuseLighting
  %stdAttrs;
  class %ClassList; #IMPLIED
  style %StyleSheet; #IMPLIED
  %PresentationAttributes-Color;
  %PresentationAttributes-FilterPrimitives;
  %PresentationAttributes-LightingEffects;
  %filter_primitive_attributes_with_in;
  surfaceScale %Number; #IMPLIED
  diffuseConstant %Number; #IMPLIED 
  kernelUnitLength %NumberOptionalNumber; #IMPLIED >

The light source is defined by one of the child elements 'feDistantLight', 'fePointLight' or 'feSpotLight'. The light color is specified by property 'lighting-color'.

15.15 Filter primitive 'feDisplacementMap'

This filter primitive uses the pixels values from the image from in2 to spatially displace the image from in. This is the transformation to be performed:

P'(x,y) <- P( x + scale * ((XC(x,y) - .5), y + scale * (YC(x,y) - .5))

where P(x,y) is the input image, in, and P'(x,y) is the destination. XC(x,y) and YC(x,y) are the component values of the designated by the xChannelSelector and yChannelSelector. For example, to use the R component of in2 to control displacement in x and the G component of Image2 to control displacement in y, set xChannelSelector to "R" and yChannelSelector to "G".

The displacement map defines the inverse of the mapping performed.

The calculations using the pixel values from in2 are performed using non-premultiplied color values. If the image from in2 consists of premultiplied color values, those values are automatically converted into non-premultiplied color values before performing this operation.

This filter can have arbitrary non-localized effect on the input which might require substantial buffering in the processing pipeline. However with this formulation, any intermediate buffering needs can be determined by scale which represents the maximum range of displacement in either x or y.

When applying this filter, the source pixel location will often lie between several source pixels. In this case it is recommended that high quality viewers apply an interpolent on the surrounding pixels, for example bilinear or bicubic, rather than simply selecting the nearest source pixel. Depending on the speed of the available interpolents, this choice may be affected by the 'image-rendering' property setting.

The 'color-interpolation-filters' property only applies to the in2 source image and does not apply to the in source image.

<!ELEMENT feDisplacementMap (animate|set)* >
<!ATTLIST feDisplacementMap
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  in2 CDATA #REQUIRED
  scale %Number; #IMPLIED
  xChannelSelector (R | G | B | A) "A"
  yChannelSelector (R | G | B | A) "A" >

15.16 Filter primitive 'feFlood'

This filter primitive creates a rectangle filled with the color and opacity values from properties 'flood-color' and 'flood-opacity'. The rectangle is as large as the filter primitive subregion established by the x, y, width and height attributes on the 'feFlood' element.

<!ELEMENT feFlood (animate|set|animateColor)* >
<!ATTLIST feFlood
  %stdAttrs;
  class %ClassList; #IMPLIED
  style %StyleSheet; #IMPLIED
  %PresentationAttributes-Color;
  %PresentationAttributes-feFlood;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in; >

The 'flood-color' property indicates what color to use to flood the current filter primitive subregion. The keyword currentColor and ICC colors can be specified in the same manner as within a <paint> specification for the 'fill' and 'stroke' properties.

The 'flood-opacity' property defines the opacity value to use across the entire filter primitive subregion.

15.17 Filter primitive 'feGaussianBlur'

This filter primitive performs a Gaussian blur on the input image.

The Gaussian blur kernel is an approximation of the normalized convolution:

H(x) = exp(-x²/ (2s²)) / sqrt(2* pi*s²)

where 's' is the standard deviation specified by stdDeviation.

The value of stdDeviation can be either one or two numbers. If two numbers are provided, the first number represents a standard deviation value along the x-axis of the current coordinate system and the second value represents a standard deviation in Y. If one number is provided, then that value is used for both X and Y.

Even if only one value is provided for stdDeviation, this can be implemented as a separable convolution.

For larger values of 's' (s >= 2.0), an approximation can be used: Three successive box-blurs build a piece-wise quadratic convolution kernel, which approximates the Gaussian kernel to within roughly 3%.

let d = floor(s * 3*sqrt(2*pi)/4 + 0.5)

... if d is odd, use three box-blurs of size 'd', centered on the output pixel.

... if d is even, two box-blurs of size 'd' (the first one centered on the pixel boundary between the output pixel and the one to the left, the second one centered on the pixel boundary between the output pixel and the one to the right) and one box blur of size 'd+1' centered on the output pixel.

Frequently this operation will take place on alpha-only images, such as that produced by the built-in input, SourceAlpha. The implementation may notice this and optimize the single channel case. If the input has infinite extent and is constant, this operation has no effect. If the input has infinite extent and is a tile, the filter is evaluated with periodic boundary conditions.

<!ELEMENT feGaussianBlur (animate|set)* >
<!ATTLIST feGaussianBlur
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  stdDeviation %NumberOptionalNumber; #IMPLIED >

The example at the start of this chapter makes use of the feGaussianBlur filter primitive to create a drop shadow effect.

15.18 Filter primitive 'feImage'

This filter primitive refers to a graphic external to this filter element, which is loaded or rendered into an RGBA raster and becomes the result of the filter primitive.

This filter primitive can refer to an external image or can be a reference to another piece of SVG. It produces an image similar to the built-in image source SourceGraphic except that the graphic comes from an external source.

If the xlink:href references a stand-alone image resource such as a JPEG, PNG or SVG file, then the image resource is rendered according to the behavior of the 'image' element; otherwise, the referenced resource is rendered according to the behavior of the 'use' element. In either case, the current user coordinate system depends on the value of attribute primitiveUnits on the 'filter' element.

When the referenced image must be resampled to match the device coordinate system, it is recommended that high quality viewers make use of appropriate interpolation techniques, for example bilinear or bicubic. Depending on the speed of the available interpolents, this choice may be affected by the 'image-rendering' property setting.

<!ELEMENT feImage (animate|set|animateTransform)* >
<!ATTLIST feImage
  %stdAttrs;
  %xlinkRefAttrsEmbed;
  xlink:href %URI; #REQUIRED
  %langSpaceAttrs;
  externalResourcesRequired %Boolean; #IMPLIED
  class %ClassList; #IMPLIED
  style %StyleSheet; #IMPLIED
  %PresentationAttributes-All; >

15.19 Filter primitive 'feMerge'

This filter primitive composites input image layers on top of each other using the over operator with Input1 (corresponding to the first 'feMergeNode' child element) on the bottom and the last specified input, InputN (corresponding to the last 'feMergeNode' child element), on top.

Many effects produce a number of intermediate layers in order to create the final output image. This filter allows us to collapse those into a single image. Although this could be done by using n-1 Composite-filters, it is more convenient to have this common operation available in this form, and offers the implementation some additional flexibility.

Each 'feMerge' element can have any number of 'feMergeNode' subelements, each of which has an in attribute.

The canonical implementation of feMerge is to render the entire effect into one RGBA layer, and then render the resulting layer on the output device. In certain cases (in particular if the output device itself is a continuous tone device), and since merging is associative, it might be a sufficient approximation to evaluate the effect one layer at a time and render each layer individually onto the output device bottom to top.

If the topmost image input is SourceGraphic and this 'feMerge' is the last filter primitive in the filter, the implementation is encouraged to render the layers up to that point, and then render the SourceGraphic directly from its vector description on top.

<!ELEMENT feMerge (feMergeNode)* >
<!ATTLIST feMerge
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes; >

<!ELEMENT feMergeNode (animate|set)* >
<!ATTLIST feMergeNode
  %stdAttrs;
  in CDATA #IMPLIED >

The example at the start of this chapter makes use of the feMerge filter primitive to composite two intermediate filter results together.

15.20 Filter primitive 'feMorphology'

This filter primitive performs "fattening" or "thinning" of artwork. It is particularly useful for fattening or thinning an alpha channel.

The dilation (or erosion) kernel is a rectangle with a width of 2*x-radius and a height of 2*y-radius. In dilation, the output pixel is the individual component-wise maximum of the corresponding R,G,B,A values in the input image's kernel rectangle. In erosion, the output pixel is the individual component-wise minimum of the corresponding R,G,B,A values in the input image's kernel rectangle.

Frequently this operation will take place on alpha-only images, such as that produced by the built-in input, SourceAlpha. In that case, the implementation might want to optimize the single channel case.

If the input has infinite extent and is constant, this operation has no effect. If the input has infinite extent and is a tile, the filter is evaluated with periodic boundary conditions.

Because 'feMorphology' operates on premultipied color values, it will always result in color values less than or equal to the alpha channel.

<!ELEMENT feMorphology (animate|set)* >
<!ATTLIST feMorphology
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  operator (erode | dilate) "erode"
  radius %NumberOptionalNumber; #IMPLIED >

Example feMorphology shows examples of the four types of feMorphology operations.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="5cm" height="7cm" viewBox="0 0 700 500" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <title>Example feMorphology - Examples of erode and dilate</title>
  <desc>Five text strings drawn as outlines.
        The first is unfiltered. The second and third use 'erode'.
        The fourth and fifth use 'dilate'.</desc>
  <defs>
    <filter id="Erode3">
      <feMorphology operator="erode" in="SourceGraphic" radius="3" />
    </filter>
    <filter id="Erode6">
      <feMorphology operator="erode" in="SourceGraphic" radius="6" />
    </filter>
    <filter id="Dilate3">
      <feMorphology operator="dilate" in="SourceGraphic" radius="3" />
    </filter>
    <filter id="Dilate6">
      <feMorphology operator="dilate" in="SourceGraphic" radius="6" />
    </filter>
  </defs>
  <rect fill="none" stroke="blue" stroke-width="2"  
        x="1" y="1" width="698" height="498"/>
  <g enable-background="new" >
    <g font-family="Verdana" font-size="75" 
              fill="none" stroke="black" stroke-width="6" >
      <text x="50" y="90">Unfiltered</text>
      <text x="50" y="180" filter="url(#Erode3)" >Erode radius 3</text>
      <text x="50" y="270" filter="url(#Erode6)" >Erode radius 6</text>
      <text x="50" y="360" filter="url(#Dilate3)" >Dilate radius 3</text>
      <text x="50" y="450" filter="url(#Dilate6)" >Dilate radius 6</text>
    </g>
  </g>
</svg>

Example feMorphology

View this example as SVG (SVG-enabled browsers only)
 

15.21 Filter primitive 'feOffset'

This filter primitive offsets the input image relative to its current position in the image space by the specified vector.

This is important for effects like drop shadows.

When applying this filter, the destination location may be offset by a fraction of a pixel in device space. In this case a high quality viewer should make use of appropriate interpolation techniques, for example bilinear or bicubic. This is especially recommended for dynamic viewers where this interpolation provides visually smoother movement of images. For static viewers this is less of a concern. Close attention should be made to the 'image-rendering' property setting to determine the authors intent.

<!ELEMENT feOffset (animate|set)* >
<!ATTLIST feOffset
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in;
  dx %Number; #IMPLIED
  dy %Number; #IMPLIED >

The example at the start of this chapter makes use of the feOffset filter primitive to offset the drop shadow from the original source graphic.

15.22 Filter primitive 'feSpecularLighting'

This filter primitive lights a source graphic using the alpha channel as a bump map. The resulting image is an RGBA image based on the light color. The lighting calculation follows the standard specular component of the Phong lighting model. The resulting image depends on the light color, light position and surface geometry of the input bump map. The result of the lighting calculation is added. The filter primitive assumes that the viewer is at infinity in the z direction (i.e., the unit vector in the eye direction is (0,0,1) everywhere).

This filter primitive produces an image which contains the specular reflection part of the lighting calculation. Such a map is intended to be combined with a texture using the add term of the arithmetic 'feComposite' method. Multiple light sources can be simulated by adding several of these light maps before applying it to the texture image.

The resulting RGBA image is computed as follows:

S_r = k_s * pow(N.H, specularExponent) * L_r
S_g = k_s * pow(N.H, specularExponent) * L_g
S_b = k_s * pow(N.H, specularExponent) * L_b
S_a = max(S_r, S_g, S_b)

where

k_s = specular lighting constant
N = surface normal unit vector, a function of x and y
H = "halfway" unit vector between eye unit vector and light unit vector

L_r,L_g,L_b = RGB components of light

See 'feDiffuseLighting' for definition of N and (L_r, L_g, L_b).

The definition of H reflects our assumption of the constant eye vector E = (0,0,1):

H = (L + E) / Norm(L+E)

where L is the light unit vector.

Unlike the 'feDiffuseLighting', the 'feSpecularLighting' filter produces a non-opaque image. This is due to the fact that the specular result (S_r,S_g,S_b,S_a) is meant to be added to the textured image. The alpha channel of the result is the max of the color components, so that where the specular light is zero, no additional coverage is added to the image and a fully white highlight will add opacity.

The 'feDiffuseLighting' and 'feSpecularLighting' filters will often be applied together. An implementation may detect this and calculate both maps in one pass, instead of two.

<!ELEMENT feSpecularLighting ((feDistantLight|fePointLight|feSpotLight),(animate|set|animateColor)*) >
<!ATTLIST feSpecularLighting
  %stdAttrs;
  class %ClassList; #IMPLIED
  style %StyleSheet; #IMPLIED
  %PresentationAttributes-Color;
  %PresentationAttributes-FilterPrimitives;
  %PresentationAttributes-LightingEffects;
  %filter_primitive_attributes_with_in;
  surfaceScale %Number; #IMPLIED
  specularConstant %Number; #IMPLIED
  specularExponent %Number; #IMPLIED 
  kernelUnitLength %NumberOptionalNumber; #IMPLIED >

The light source is defined by one of the child elements 'feDistantLight', 'fePointLight' or 'feDistantLight'. The light color is specified by property 'lighting-color'.

The example at the start of this chapter makes use of the feSpecularLighting filter primitive to achieve a highly reflective, 3D glowing effect.

15.23 Filter primitive 'feTile'

This filter primitive fills a target rectangle with a repeated, tiled pattern of an input image. The target rectangle is as large as the filter primitive subregion established by the x, y, width and height attributes on the 'feTile' element.

Typically, the input image has been defined with its own filter primitive subregion in order to define a reference tile. 'feTile' replicates the reference tile in both X and Y to completely fill the target rectangle. The top/left corner of each given tile is at location (x+i*width,y+j*height), where (x,y) represents the top/left of the input image's filter primitive subregion, width and height represent the width and height of the input image's filter primitive subregion, and i and j can be any integer value. In most cases, the input image will have a smaller filter primitive subregion than the 'feTile' in order to achieve a repeated pattern effect.

Implementers must take appropriate measures in constructing the tiled image to avoid artifacts between tiles, particularly in situations where the user to device transform includes shear and/or rotation. Unless care is taken, interpolation can lead to edge pixels in the tile having opacity values lower or higher than expected due to the interaction of painting adjacent tiles which each have partial overlap with particular pixels.

<!ELEMENT feTile (animate|set)* >
<!ATTLIST feTile
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes_with_in; >

15.24 Filter primitive 'feTurbulence'

This filter primitive creates an image using the Perlin turbulence function. It allows the synthesis of artificial textures like clouds or marble. For a detailed description the of the Perlin turbulence function, see "Texturing and Modeling", Ebert et al, AP Professional, 1994. The resulting image will fill the entire filter primitive subregion for this filter primitive.

It is possible to create bandwidth-limited noise by synthesizing only one octave.

The C code below shows the exact algorithm used for this filter effect.

For fractalSum, you get a turbFunctionResult that is aimed at a range of -1 to 1 (the actual result might exceed this range in some cases). To convert to a color value, use the formula colorValue = ((turbFunctionResult * 255) + 255) / 2, then clamp to the range 0 to 255.

For turbulence, you get a turbFunctionResult that is aimed at a range of 0 to 1 (the actual result might exceed this range in some cases). To convert to a color value, use the formula colorValue = (turbFunctionResult * 255), then clamp to the range 0 to 255.

The following order is used for applying the pseudo random numbers. An initial seed value is computed based on attribute seed. Then the implementation computes the lattice points for R, then continues getting additional pseudo random numbers relative to the last generated pseudo random number and computes the lattice points for G, and so on for B and A.

The generated color and alpha values are in the color space determined by the value of property 'color-interpolation-filters':

/* Produces results in the range [1, 2**31 - 2].
Algorithm is: r = (a * r) mod m
where a = 16807 and m = 2**31 - 1 = 2147483647
See [Park & Miller], CACM vol. 31 no. 10 p. 1195, Oct. 1988
To test: the algorithm should produce the result 1043618065
as the 10,000th generated number if the original seed is 1.
*/
#define RAND_m 2147483647 /* 2**31 - 1 */
#define RAND_a 16807 /* 7**5; primitive root of m */
#define RAND_q 127773 /* m / a */
#define RAND_r 2836 /* m % a */

long setup_seed(long lSeed)
{
  if (lSeed <= 0) lSeed = -(lSeed % (RAND_m - 1)) + 1;
  if (lSeed > RAND_m - 1) lSeed = RAND_m - 1;
  return lSeed;
}

long random(long lSeed)
{
  long result;
  result = RAND_a * (lSeed % RAND_q) - RAND_r * (lSeed / RAND_q);
  if (result <= 0) result += RAND_m;
  return result;
}

#define BSize 0x100
#define BM 0xff
#define PerlinN 0x1000
#define NP 12 /* 2^PerlinN */
#define NM 0xfff
static uLatticeSelector[BSize + BSize + 2];
static double fGradient[4][BSize + BSize + 2][2];
struct StitchInfo
{
  int nWidth; // How much to subtract to wrap for stitching.
  int nHeight;
  int nWrapX; // Minimum value to wrap.
  int nWrapY;
};

static void init(long lSeed)
{
  double s;
  int i, j, k;
  lSeed = setup_seed(lSeed);
  for(k = 0; k < 4; k++)
  {
    for(i = 0; i < BSize; i++)
    {
      uLatticeSelector[i] = i;
      for (j = 0; j < 2; j++)
        fGradient[k][i][j] = (double)(((lSeed = random(lSeed)) % (BSize + BSize)) - BSize) / BSize;
      s = double(sqrt(fGradient[k][i][0] * fGradient[k][i][0] + fGradient[k][i][1] * fGradient[k][i][1]));
      fGradient[k][i][0] /= s;
      fGradient[k][i][1] /= s;
    }
  }
  while(--i)
  {
    k = uLatticeSelector[i];
    uLatticeSelector[i] = uLatticeSelector[j = (lSeed = random(lSeed)) % BSize];
    uLatticeSelector[j] = k;
  }
  for(i = 0; i < BSize + 2; i++)
  {
    uLatticeSelector[BSize + i] = uLatticeSelector[i];
    for(k = 0; k < 4; k++)
      for(j = 0; j < 2; j++)
        fGradient[k][BSize + i][j] = fGradient[k][i][j];
  }
}

#define s_curve(t) ( t * t * (3. - 2. * t) )
#define lerp(t, a, b) ( a + t * (b - a) )
double noise2(int nColorChannel, double vec[2], StitchInfo *pStitchInfo)
{
  int bx0, bx1, by0, by1, b00, b10, b01, b11;
  double rx0, rx1, ry0, ry1, *q, sx, sy, a, b, t, u, v;
  register i, j;
  t = vec[0] + PerlinN;
  bx0 = (int)t;
  bx1 = bx0+1;
  rx0 = t - (int)t;
  rx1 = rx0 - 1.0f;
  t = vec[1] + PerlinN;
  by0 = (int)t;
  by1 = by0+1;
  ry0 = t - (int)t;
  ry1 = ry0 - 1.0f;

  // If stitching, adjust lattice points accordingly.
  if(pStitchInfo != NULL)
  {
    if(bx0 >= pStitchInfo->nWrapX)
      bx0 -= pStitchInfo->nWidth;
    if(bx1 >= pStitchInfo->nWrapX)
      bx1 -= pStitchInfo->nWidth;
    if(by0 >= pStitchInfo->nWrapY)
      by0 -= pStitchInfo->nHeight;
    if(by1 >= pStitchInfo->nWrapY)
      by1 -= pStitchInfo->nHeight;
  }

  bx0 &= BM;
  bx1 &= BM;
  by0 &= BM;
  by1 &= BM;

  i = uLatticeSelector[bx0];
  j = uLatticeSelector[bx1];
  b00 = uLatticeSelector[i + by0];
  b10 = uLatticeSelector[j + by0];
  b01 = uLatticeSelector[i + by1];
  b11 = uLatticeSelector[j + by1];
  sx = double(s_curve(rx0));
  sy = double(s_curve(ry0));
  q = fGradient[nColorChannel][b00]; u = rx0 * q[0] + ry0 * q[1];
  q = fGradient[nColorChannel][b10]; v = rx1 * q[0] + ry0 * q[1];
  a = lerp(sx, u, v);
  q = fGradient[nColorChannel][b01]; u = rx0 * q[0] + ry1 * q[1];
  q = fGradient[nColorChannel][b11]; v = rx1 * q[0] + ry1 * q[1];
  b = lerp(sx, u, v);
  return lerp(sy, a, b);
}

double turbulence(int nColorChannel, double *point, double fBaseFreqX, double fBaseFreqY,
          int nNumOctaves, bool bFractalSum, bool bDoStitching,
          double fTileX, double fTileY, double fTileWidth, double fTileHeight)
{
  StitchInfo stitch;
  StitchInfo *pStitchInfo = NULL; // Not stitching when NULL.

  // Adjust the base frequencies if necessary for stitching.
  if(bDoStitching)
  {
    // When stitching tiled turbulence, the frequencies must be adjusted
    // so that the tile borders will be continuous.
    if(fBaseFreqX != 0.0)
    {
      double fLoFreq = double(floor(fTileWidth * fBaseFreqX)) / fTileWidth;
      double fHiFreq = double(ceil(fTileWidth * fBaseFreqX)) / fTileWidth;
      if(fBaseFreqX / fLoFreq < fHiFreq / fBaseFreqX)
        fBaseFreqX = fLoFreq;
      else
        fBaseFreqX = fHiFreq;
    }

    if(fBaseFreqY != 0.0)
    {
      double fLoFreq = double(floor(fTileHeight * fBaseFreqY)) / fTileHeight;
      double fHiFreq = double(ceil(fTileHeight * fBaseFreqY)) / fTileHeight;
      if(fBaseFreqY / fLoFreq < fHiFreq / fBaseFreqY)
        fBaseFreqY = fLoFreq;
      else
        fBaseFreqY = fHiFreq;
    }

    // Set up initial stitch values.
    pStitchInfo = &stitch;
    stitch.nWidth = int(fTileWidth * fBaseFreqX + 0.5f);
    stitch.nWrapX = fTileX * fBaseFreqX + PerlinN + stitch.nWidth;
    stitch.nHeight = int(fTileHeight * fBaseFreqY + 0.5f);
    stitch.nWrapY = fTileY * fBaseFreqY + PerlinN + stitch.nHeight;
  }

  double fSum = 0.0f;
  double vec[2];
  vec[0] = point[0] * fBaseFreqX;
  vec[1] = point[1] * fBaseFreqY;
  double ratio = 1;
  for(int nOctave = 0; nOctave < nNumOctaves; nOctave++)
  {
    if(bFractalSum)
      fSum += double(noise2(nColorChannel, vec, pStitchInfo) / ratio);
    else
      fSum += double(fabs(noise2(nColorChannel, vec, pStitchInfo)) / ratio);

    vec[0] *= 2;
    vec[1] *= 2;
    ratio *= 2;

    if(pStitchInfo != NULL)
    {
      // Update stitch values. Subtracting PerlinN before the multiplication and
      // adding it afterward simplifies to subtracting it once.
      stitch.nWidth *= 2;
      stitch.nWrapX = 2 * stitch.nWrapX - PerlinN;
      stitch.nHeight *= 2;
      stitch.nWrapY = 2 * stitch.nWrapY - PerlinN;
    }
  }
  return fSum;
}

<!ELEMENT feTurbulence (animate|set)* >
<!ATTLIST feTurbulence
  %stdAttrs;
  %PresentationAttributes-FilterPrimitives;
  %filter_primitive_attributes;
  baseFrequency %NumberOptionalNumber; #IMPLIED
  numOctaves %Integer; #IMPLIED
  seed %Number; #IMPLIED
  stitchTiles (stitch | noStitch) "noStitch"
  type (fractalNoise | turbulence) "turbulence" >

Example feTurbulence shows the effects of various parameter settings for feTurbulence.

<?xml version="1.0"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
          "http://www.w3.org/TR/2002/WD-SVG11-20020215/DTD/svg11.dtd">
<svg width="450px" height="325px" viewBox="0 0 450 325" version="1.1"
     xmlns="http://www.w3.org/2000/svg">
  <title>Example feTurbulence - Examples of feTurbulence operations</title>
  <desc>Six rectangular areas showing the effects of 
        various parameter settings for feTurbulence.</desc>
  <g  font-family="Verdana" text-anchor="middle" font-size="10" >
    <defs>
      <filter id="Turb1" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.05" numOctaves="2"/>
      </filter>
      <filter id="Turb2" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.1" numOctaves="2"/>
      </filter>
      <filter id="Turb3" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="turbulence" baseFrequency="0.05" numOctaves="8"/>
      </filter>
      <filter id="Turb4" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.1" numOctaves="4"/>
      </filter>
      <filter id="Turb5" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.4" numOctaves="4"/>
      </filter>
      <filter id="Turb6" filterUnits="objectBoundingBox" 
              x="0%" y="0%" width="100%" height="100%">
        <feTurbulence type="fractalNoise" baseFrequency="0.1" numOctaves="1"/>
      </filter>
    </defs>

    <rect x="1" y="1" width="448" height="323"
          fill="none" stroke="blue" stroke-width="1"  />

    <rect x="25" y="25" width="100" height="75" filter="url(#Turb1)"  />
    <text x="75" y="117">type=turbulence</text>
    <text x="75" y="129">baseFrequency=0.05</text>
    <text x="75" y="141">numOctaves=2</text>

    <rect x="175" y="25" width="100" height="75" filter="url(#Turb2)"  />
    <text x="225" y="117">type=turbulence</text>
    <text x="225" y="129">baseFrequency=0.1</text>
    <text x="225" y="141">numOctaves=2</text>

    <rect x="325" y="25" width="100" height="75" filter="url(#Turb3)"  />
    <text x="375" y="117">type=turbulence</text>
    <text x="375" y="129">baseFrequency=0.05</text>
    <text x="375" y="141">numOctaves=8</text>

    <rect x="25" y="180" width="100" height="75" filter="url(#Turb4)"  />
    <text x="75" y="272">type=fractalNoise</text>
    <text x="75" y="284">baseFrequency=0.1</text>
    <text x="75" y="296">numOctaves=4</text>

    <rect x="175" y="180" width="100" height="75" filter="url(#Turb5)"  />
    <text x="225" y="272">type=fractalNoise</text>
    <text x="225" y="284">baseFrequency=0.4</text>
    <text x="225" y="296">numOctaves=4</text>

    <rect x="325" y="180" width="100" height="75" filter="url(#Turb6)"  />
    <text x="375" y="272">type=fractalNoise</text>
    <text x="375" y="284">baseFrequency=0.1</text>
    <text x="375" y="296">numOctaves=1</text>
  </g>
</svg>

Example feTurbulence

View this example as SVG (SVG-enabled browsers only)
 

15.27 DOM interfaces

The following interfaces are defined below: SVGFilterElement, SVGFilterPrimitiveStandardAttributes, SVGFEBlendElement, SVGFEColorMatrixElement, SVGFEComponentTransferElement, SVGComponentTransferFunctionElement, SVGFEFuncRElement, SVGFEFuncGElement, SVGFEFuncBElement, SVGFEFuncAElement, SVGFECompositeElement, SVGFEConvolveMatrixElement, SVGFEDiffuseLightingElement, SVGFEDistantLightElement, SVGFEPointLightElement, SVGFESpotLightElement, SVGFEDisplacementMapElement, SVGFEFloodElement, SVGFEGaussianBlurElement, SVGFEImageElement, SVGFEMergeElement, SVGFEMergeNodeElement, SVGFEMorphologyElement, SVGFEOffsetElement, SVGFESpecularLightingElement, SVGFETileElement, SVGFETurbulenceElement.

Interface SVGFilterElement

The SVGFilterElement interface corresponds to the 'filter' element.

IDL Definition

interface SVGFilterElement : 
                SVGElement,
                SVGURIReference,
                SVGLangSpace,
                SVGExternalResourcesRequired,
                SVGStylable,
                SVGUnitTypes { 

  readonly attribute SVGAnimatedEnumeration filterUnits;
  readonly attribute SVGAnimatedEnumeration primitiveUnits;
  readonly attribute SVGAnimatedLength      x;
  readonly attribute SVGAnimatedLength      y;
  readonly attribute SVGAnimatedLength      width;
  readonly attribute SVGAnimatedLength      height;
  readonly attribute SVGAnimatedInteger    filterResX;
  readonly attribute SVGAnimatedInteger    filterResY;

  void setFilterRes ( in unsigned long filterResX, in unsigned long filterResY );
};

Attributes

readonly SVGAnimatedEnumeration filterUnits

Corresponds to attribute filterUnits on the given 'filter' element. Takes one of the constants defined in SVGUnitTypes.

readonly SVGAnimatedEnumeration primitiveUnits

Corresponds to attribute primitiveUnits on the given 'filter' element. Takes one of the constants defined in SVGUnitTypes.

readonly SVGAnimatedLength x

Corresponds to attribute x on the given 'filter' element.

readonly SVGAnimatedLength y

Corresponds to attribute y on the given 'filter' element.

readonly SVGAnimatedLength width

Corresponds to attribute width on the given 'filter' element.

readonly SVGAnimatedLength height

Corresponds to attribute height on the given 'filter' element.

readonly SVGAnimatedInteger filterResX

Corresponds to attribute filterRes on the given 'filter' element. Contains the X component of attribute filterRes.

readonly SVGAnimatedInteger filterResY

Corresponds to attribute filterRes on the given 'filter' element. Contains the Y component (possibly computed automatically) of attribute filterRes.

Methods

setFilterRes

Sets the values for attribute filterRes.

Parameters

in unsigned long filterResX		The X component of attribute filterRes.
in unsigned long filterResY		The Y component of attribute filterRes.

No Return Value

No Exceptions

Interface SVGFilterPrimitiveStandardAttributes

This interface defines the set of DOM attributes that are common across the filter interfaces.

IDL Definition

interface SVGFilterPrimitiveStandardAttributes : SVGStylable { 
  readonly attribute SVGAnimatedLength x;
  readonly attribute SVGAnimatedLength y;
  readonly attribute SVGAnimatedLength width;
  readonly attribute SVGAnimatedLength height;
  readonly attribute SVGAnimatedString result;
};

Attributes

readonly SVGAnimatedLength x

Corresponds to attribute x on the given element.

readonly SVGAnimatedLength y

Corresponds to attribute y on the given element.

readonly SVGAnimatedLength width

Corresponds to attribute width on the given element.

readonly SVGAnimatedLength height

Corresponds to attribute height on the given element.

readonly SVGAnimatedString result

Corresponds to attribute result on the given element.

Interface SVGFEBlendElement

The SVGFEBlendElement interface corresponds to the 'feBlend' element.

IDL Definition

interface SVGFEBlendElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Blend Mode Types
  const unsigned short SVG_FEBLEND_MODE_UNKNOWN  = 0;
  const unsigned short SVG_FEBLEND_MODE_NORMAL   = 1;
  const unsigned short SVG_FEBLEND_MODE_MULTIPLY = 2;
  const unsigned short SVG_FEBLEND_MODE_SCREEN   = 3;
  const unsigned short SVG_FEBLEND_MODE_DARKEN   = 4;
  const unsigned short SVG_FEBLEND_MODE_LIGHTEN  = 5;

  readonly attribute SVGAnimatedString      in1;
  readonly attribute SVGAnimatedString      in2;
  readonly attribute SVGAnimatedEnumeration mode;
};

Definition group Blend Mode Types

Defined constants

SVG_FEBLEND_MODE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_FEBLEND_MODE_NORMAL		Corresponds to value normal.
SVG_FEBLEND_MODE_MULTIPLY		Corresponds to value multiply.
SVG_FEBLEND_MODE_SCREEN		Corresponds to value screen.
SVG_FEBLEND_MODE_DARKEN		Corresponds to value darken.
SVG_FEBLEND_MODE_LIGHTEN		Corresponds to value lighten.

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feBlend' element.

readonly SVGAnimatedString in2

Corresponds to attribute in2 on the given 'feBlend' element.

readonly SVGAnimatedEnumeration mode

Corresponds to attribute mode on the given 'feBlend' element. Takes one of the Blend Mode Types.

Interface SVGFEColorMatrixElement

The SVGFEColorMatrixElement interface corresponds to the 'feColorMatrix' element.

IDL Definition

interface SVGFEColorMatrixElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Color Matrix Types
  const unsigned short SVG_FECOLORMATRIX_TYPE_UNKNOWN          = 0;
  const unsigned short SVG_FECOLORMATRIX_TYPE_MATRIX           = 1;
  const unsigned short SVG_FECOLORMATRIX_TYPE_SATURATE         = 2;
  const unsigned short SVG_FECOLORMATRIX_TYPE_HUEROTATE        = 3;
  const unsigned short SVG_FECOLORMATRIX_TYPE_LUMINANCETOALPHA = 4;

  readonly attribute SVGAnimatedString      in1;
  readonly attribute SVGAnimatedEnumeration type;
  readonly attribute SVGAnimatedNumberList  values;
};

Definition group Color Matrix Types

Defined constants

SVG_FECOLORMATRIX_TYPE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_FECOLORMATRIX_TYPE_MATRIX		Corresponds to value matrix.
SVG_FECOLORMATRIX_TYPE_SATURATE		Corresponds to value saturate.
SVG_FECOLORMATRIX_TYPE_HUEROTATE		Corresponds to value hueRotate.
SVG_FECOLORMATRIX_TYPE_LUMINANCETOALPHA		Corresponds to value luminanceToAlpha.

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feColorMatrix' element.

readonly SVGAnimatedEnumeration type

Corresponds to attribute type on the given 'feColorMatrix' element. Takes one of the Color Matrix Types.

readonly SVGAnimatedNumberList values

Corresponds to attribute values on the given 'feColorMatrix' element.

Provides access to the contents of the values attribute.

Interface SVGFEComponentTransferElement

The SVGFEComponentTransferElement interface corresponds to the 'feComponentTransfer' element.

IDL Definition

interface SVGFEComponentTransferElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feComponentTransfer' element.

Interface SVGComponentTransferFunctionElement

This interface defines a base interface used by the component transfer function interfaces.

IDL Definition

interface SVGComponentTransferFunctionElement : SVGElement { 
  // Component Transfer Types
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_UNKNOWN  = 0;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_IDENTITY = 1;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_TABLE    = 2;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_DISCRETE    = 3;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_LINEAR   = 4;
  const unsigned short SVG_FECOMPONENTTRANSFER_TYPE_GAMMA    = 5;

  readonly attribute SVGAnimatedEnumeration type;
  readonly attribute SVGAnimatedNumberList  tableValues;
  readonly attribute SVGAnimatedNumber      slope;
  readonly attribute SVGAnimatedNumber      intercept;
  readonly attribute SVGAnimatedNumber      amplitude;
  readonly attribute SVGAnimatedNumber      exponent;
  readonly attribute SVGAnimatedNumber      offset;
};

Definition group Component Transfer Types

Defined constants

SVG_FECOMPONENTTRANSFER_TYPE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_FECOMPONENTTRANSFER_TYPE_IDENTITY		Corresponds to value identity.
SVG_FECOMPONENTTRANSFER_TYPE_TABLE		Corresponds to value table.
SVG_FECOMPONENTTRANSFER_TYPE_DISCRETE		Corresponds to value discrete.
SVG_FECOMPONENTTRANSFER_TYPE_LINEAR		Corresponds to value linear.
SVG_FECOMPONENTTRANSFER_TYPE_GAMMA		Corresponds to value gamma.

Attributes

readonly SVGAnimatedEnumeration type

Corresponds to attribute type on the given element. Takes one of the Component Transfer Types.

readonly SVGAnimatedNumberList tableValues

Corresponds to attribute tableValues on the given element.

readonly SVGAnimatedNumber slope

Corresponds to attribute slope on the given element.

readonly SVGAnimatedNumber intercept

Corresponds to attribute intercept on the given element.

readonly SVGAnimatedNumber amplitude

Corresponds to attribute amplitude on the given element.

readonly SVGAnimatedNumber exponent

Corresponds to attribute exponent on the given element.

readonly SVGAnimatedNumber offset

Corresponds to attribute offset on the given element.

Interface SVGFEFuncRElement

The SVGFEFuncRElement interface corresponds to the 'feFuncR' element.

IDL Definition

interface SVGFEFuncRElement : SVGComponentTransferFunctionElement {};

Interface SVGFEFuncGElement

The SVGFEFuncGElement interface corresponds to the 'feFuncG' element.

IDL Definition

interface SVGFEFuncGElement : SVGComponentTransferFunctionElement {};

Interface SVGFEFuncBElement

The SVGFEFuncBElement interface corresponds to the 'feFuncB' element.

IDL Definition

interface SVGFEFuncBElement : SVGComponentTransferFunctionElement {};

Interface SVGFEFuncAElement

The SVGFEFuncAElement interface corresponds to the 'feFuncA' element.

IDL Definition

interface SVGFEFuncAElement : SVGComponentTransferFunctionElement {};

Interface SVGFECompositeElement

The SVGFECompositeElement interface corresponds to the 'feComposite' element.

IDL Definition

interface SVGFECompositeElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Composite Operators
  const unsigned short SVG_FECOMPOSITE_OPERATOR_UNKNOWN    = 0;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_OVER       = 1;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_IN         = 2;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_OUT        = 3;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_ATOP       = 4;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_XOR        = 5;
  const unsigned short SVG_FECOMPOSITE_OPERATOR_ARITHMETIC = 6;

  readonly attribute SVGAnimatedString      in1;
  readonly attribute SVGAnimatedString      in2;
  readonly attribute SVGAnimatedEnumeration operator;
  readonly attribute SVGAnimatedNumber      k1;
  readonly attribute SVGAnimatedNumber      k2;
  readonly attribute SVGAnimatedNumber      k3;
  readonly attribute SVGAnimatedNumber      k4;
};

Definition group Composite Operators

Defined constants

SVG_FECOMPOSITE_OPERATOR_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_FECOMPOSITE_OPERATOR_OVER		Corresponds to value over.
SVG_FECOMPOSITE_OPERATOR_IN		Corresponds to value in.
SVG_FECOMPOSITE_OPERATOR_OUT		Corresponds to value out.
SVG_FECOMPOSITE_OPERATOR_ATOP		Corresponds to value atop.
SVG_FECOMPOSITE_OPERATOR_XOR		Corresponds to value xor.
SVG_FECOMPOSITE_OPERATOR_ARITHMETIC		Corresponds to value arithmetic.

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feComposite' element.

readonly SVGAnimatedString in2

Corresponds to attribute in2 on the given 'feComposite' element.

readonly SVGAnimatedEnumeration operator

Corresponds to attribute operator on the given 'feComposite' element. Takes one of the Composite Operators.

readonly SVGAnimatedNumber k1

Corresponds to attribute k1 on the given 'feComposite' element.

readonly SVGAnimatedNumber k2

Corresponds to attribute k2 on the given 'feComposite' element.

readonly SVGAnimatedNumber k3

Corresponds to attribute k3 on the given 'feComposite' element.

readonly SVGAnimatedNumber k4

Corresponds to attribute k4 on the given 'feComposite' element.

Interface SVGFEConvolveMatrixElement

The SVGFEConvolveMatrixElement interface corresponds to the 'feConvolveMatrix' element.

IDL Definition

interface SVGFEConvolveMatrixElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Edge Mode Values
  const unsigned short SVG_EDGEMODE_UNKNOWN   = 0;
  const unsigned short SVG_EDGEMODE_DUPLICATE = 1;
  const unsigned short SVG_EDGEMODE_WRAP      = 2;
  const unsigned short SVG_EDGEMODE_NONE      = 3;

  readonly attribute SVGAnimatedInteger     orderX;
  readonly attribute SVGAnimatedInteger     orderY;
  readonly attribute SVGAnimatedNumberList  kernelMatrix;
  readonly attribute SVGAnimatedNumber      divisor;
  readonly attribute SVGAnimatedNumber      bias;
  readonly attribute SVGAnimatedInteger     targetX;
  readonly attribute SVGAnimatedInteger     targetY;
  readonly attribute SVGAnimatedEnumeration edgeMode;
  readonly attribute SVGAnimatedLength      kernelUnitLengthX;
  readonly attribute SVGAnimatedLength      kernelUnitLengthY;
  readonly attribute SVGAnimatedBoolean     preserveAlpha;
};

Definition group Edge Mode Values

Defined constants

SVG_EDGEMODE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_EDGEMODE_DUPLICATE		Corresponds to value duplicate.
SVG_EDGEMODE_WRAP		Corresponds to value wrap.
SVG_EDGEMODE_NONE		Corresponds to value none.

Attributes

readonly SVGAnimatedInteger orderX

Corresponds to attribute order on the given 'feConvolveMatrix' element.

readonly SVGAnimatedInteger orderY

Corresponds to attribute order on the given 'feConvolveMatrix' element.

readonly SVGAnimatedNumberList kernelMatrix

Corresponds to attribute kernelMatrix on the given element.

readonly SVGAnimatedNumber divisor

Corresponds to attribute divisor on the given 'feConvolveMatrix' element.

readonly SVGAnimatedNumber bias

Corresponds to attribute bias on the given 'feConvolveMatrix' element.

readonly SVGAnimatedInteger targetX

Corresponds to attribute targetX on the given 'feConvolveMatrix' element.

readonly SVGAnimatedInteger targetY

Corresponds to attribute targetY on the given 'feConvolveMatrix' element.

readonly SVGAnimatedEnumeration edgeMode

Corresponds to attribute edgeMode on the given 'feConvolveMatrix' element. Takes one of the Edge Mode Types.

readonly SVGAnimatedLength kernelUnitLengthX

Corresponds to attribute kernelUnitLength on the given 'feConvolveMatrix' element.

readonly SVGAnimatedLength kernelUnitLengthY

Corresponds to attribute kernelUnitLength on the given 'feConvolveMatrix' element.

readonly SVGAnimatedBoolean preserveAlpha

Corresponds to attribute preserveAlpha on the given 'feConvolveMatrix' element.

Interface SVGFEDiffuseLightingElement

The SVGFEDiffuseLightingElement interface corresponds to the 'feDiffuseLighting' element.

IDL Definition

interface SVGFEDiffuseLightingElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber surfaceScale;
  readonly attribute SVGAnimatedNumber diffuseConstant;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feDiffuseLighting' element.

readonly SVGAnimatedNumber surfaceScale

Corresponds to attribute surfaceScale on the given 'feDiffuseLighting' element.

readonly SVGAnimatedNumber diffuseConstant

Corresponds to attribute diffuseConstant on the given 'feDiffuseLighting' element.

Interface SVGFEDistantLightElement

The SVGFEDistantLightElement interface corresponds to the 'feDistantLight' element.

IDL Definition

interface SVGFEDistantLightElement : SVGElement { 
  readonly attribute SVGAnimatedNumber azimuth;
  readonly attribute SVGAnimatedNumber elevation;
};

Attributes

readonly SVGAnimatedNumber azimuth

Corresponds to attribute azimuth on the given 'feDistantLight' element.

readonly SVGAnimatedNumber elevation

Corresponds to attribute elevation on the given 'feDistantLight' element.

Interface SVGFEPointLightElement

The SVGFEPointLightElement interface corresponds to the 'fePointLight' element.

IDL Definition

interface SVGFEPointLightElement : SVGElement { 
  readonly attribute SVGAnimatedNumber x;
  readonly attribute SVGAnimatedNumber y;
  readonly attribute SVGAnimatedNumber z;
};

Attributes

readonly SVGAnimatedNumber x

Corresponds to attribute x on the given 'fePointLight' element.

readonly SVGAnimatedNumber y

Corresponds to attribute y on the given 'fePointLight' element.

readonly SVGAnimatedNumber z

Corresponds to attribute z on the given 'fePointLight' element.

Interface SVGFESpotLightElement

The SVGFESpotLightElement interface corresponds to the 'feSpotLight' element.

IDL Definition

interface SVGFESpotLightElement : SVGElement { 
  readonly attribute SVGAnimatedNumber x;
  readonly attribute SVGAnimatedNumber y;
  readonly attribute SVGAnimatedNumber z;
  readonly attribute SVGAnimatedNumber pointsAtX;
  readonly attribute SVGAnimatedNumber pointsAtY;
  readonly attribute SVGAnimatedNumber pointsAtZ;
  readonly attribute SVGAnimatedNumber specularExponent;
  readonly attribute SVGAnimatedNumber limitingConeAngle;
};

Attributes

readonly SVGAnimatedNumber x

Corresponds to attribute x on the given 'feSpotLight' element.

readonly SVGAnimatedNumber y

Corresponds to attribute y on the given 'feSpotLight' element.

readonly SVGAnimatedNumber z

Corresponds to attribute z on the given 'feSpotLight' element.

readonly SVGAnimatedNumber pointsAtX

Corresponds to attribute pointsAtX on the given 'feSpotLight' element.

readonly SVGAnimatedNumber pointsAtY

Corresponds to attribute pointsAtY on the given 'feSpotLight' element.

readonly SVGAnimatedNumber pointsAtZ

Corresponds to attribute pointsAtZ on the given 'feSpotLight' element.

readonly SVGAnimatedNumber specularExponent

Corresponds to attribute specularExponent on the given 'feSpotLight' element.

readonly SVGAnimatedNumber limitingConeAngle

Corresponds to attribute limitingConeAngle on the given 'feSpotLight' element.

Interface SVGFEDisplacementMapElement

The SVGFEDisplacementMapElement interface corresponds to the 'feDisplacementMap' element.

IDL Definition

interface SVGFEDisplacementMapElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Channel Selectors
  const unsigned short SVG_CHANNEL_UNKNOWN = 0;
  const unsigned short SVG_CHANNEL_R       = 1;
  const unsigned short SVG_CHANNEL_G       = 2;
  const unsigned short SVG_CHANNEL_B       = 3;
  const unsigned short SVG_CHANNEL_A       = 4;

  readonly attribute SVGAnimatedString      in1;
  readonly attribute SVGAnimatedString      in2;
  readonly attribute SVGAnimatedNumber      scale;
  readonly attribute SVGAnimatedEnumeration xChannelSelector;
  readonly attribute SVGAnimatedEnumeration yChannelSelector;
};

Definition group Channel Selectors

Defined constants

SVG_CHANNEL_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_CHANNEL_R		Corresponds to value R.
SVG_CHANNEL_G		Corresponds to value G.
SVG_CHANNEL_B		Corresponds to value B.
SVG_CHANNEL_A		Corresponds to value A.

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feDisplacementMap' element.

readonly SVGAnimatedString in2

Corresponds to attribute in2 on the given 'feDisplacementMap' element.

readonly SVGAnimatedNumber scale

Corresponds to attribute scale on the given 'feDisplacementMap' element.

readonly SVGAnimatedEnumeration xChannelSelector

Corresponds to attribute xChannelSelector on the given 'feDisplacementMap' element. Takes one of the Channel Selectors.

readonly SVGAnimatedEnumeration yChannelSelector

Corresponds to attribute yChannelSelector on the given 'feDisplacementMap' element. Takes one of the Channel Selectors.

Interface SVGFEFloodElement

The SVGFEFloodElement interface corresponds to the 'feFlood' element.

IDL Definition

interface SVGFEFloodElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString      in1;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feFlood' element.

Interface SVGFEGaussianBlurElement

The SVGFEGaussianBlurElement interface corresponds to the 'feGaussianBlur' element.

IDL Definition

interface SVGFEGaussianBlurElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber stdDeviationX;
  readonly attribute SVGAnimatedNumber stdDeviationY;

  void setStdDeviation ( in float stdDeviationX, in float stdDeviationY );
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feGaussianBlur' element.

readonly SVGAnimatedNumber stdDeviationX

Corresponds to attribute stdDeviation on the given 'feGaussianBlur' element. Contains the X component of attribute stdDeviation.

readonly SVGAnimatedNumber stdDeviationY

Corresponds to attribute stdDeviation on the given 'feGaussianBlur' element. Contains the Y component (possibly computed automatically) of attribute stdDeviation.

Methods

setStdDeviation

Sets the values for attribute stdDeviation.

Parameters

in float stdDeviationX		The X component of attribute stdDeviation.
in float stdDeviationY		The Y component of attribute stdDeviation.

No Return Value

No Exceptions

Interface SVGFEImageElement

The SVGFEImageElement interface corresponds to the 'feImage' element.

IDL Definition

interface SVGFEImageElement : 
                SVGElement,
                SVGURIReference,
                SVGLangSpace,
                SVGExternalResourcesRequired,
                SVGFilterPrimitiveStandardAttributes {};

Interface SVGFEMergeElement

The SVGFEMergeElement interface corresponds to the 'feMerge' element.

IDL Definition

interface SVGFEMergeElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes {};

Interface SVGFEMergeNodeElement

The SVGFEMergeNodeElement interface corresponds to the 'feMergeNode' element.

IDL Definition

interface SVGFEMergeNodeElement : SVGElement { 
  readonly attribute SVGAnimatedString in1;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feMergeNode' element.

Interface SVGFEMorphologyElement

The SVGFEMorphologyElement interface corresponds to the 'feMorphology' element.

IDL Definition

interface SVGFEMorphologyElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Morphology Operators
  const unsigned short SVG_MORPHOLOGY_OPERATOR_UNKNOWN = 0;
  const unsigned short SVG_MORPHOLOGY_OPERATOR_ERODE   = 1;
  const unsigned short SVG_MORPHOLOGY_OPERATOR_DILATE  = 2;

  readonly attribute SVGAnimatedString      in1;
  readonly attribute SVGAnimatedEnumeration operator;
  readonly attribute SVGAnimatedLength      radiusX;
  readonly attribute SVGAnimatedLength      radiusY;
};

Definition group Morphology Operators

Defined constants

SVG_MORPHOLOGY_OPERATOR_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_MORPHOLOGY_OPERATOR_ERODE		Corresponds to value erode.
SVG_MORPHOLOGY_OPERATOR_DILATE		Corresponds to value dilate.

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feMorphology' element.

readonly SVGAnimatedEnumeration operator

Corresponds to attribute operator on the given 'feMorphology' element. Takes one of the Morphology Operators.

readonly SVGAnimatedLength radiusX

Corresponds to attribute radius on the given 'feMorphology' element.

readonly SVGAnimatedLength radiusY

Corresponds to attribute radius on the given 'feMorphology' element.

Interface SVGFEOffsetElement

The SVGFEOffsetElement interface corresponds to the 'feOffset' element.

IDL Definition

interface SVGFEOffsetElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber dx;
  readonly attribute SVGAnimatedNumber dy;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feOffset' element.

readonly SVGAnimatedNumber dx

Corresponds to attribute dx on the given 'feOffset' element.

readonly SVGAnimatedNumber dy

Corresponds to attribute dy on the given 'feOffset' element.

Interface SVGFESpecularLightingElement

The SVGFESpecularLightingElement interface corresponds to the 'feSpecularLighting' element.

IDL Definition

interface SVGFESpecularLightingElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
  readonly attribute SVGAnimatedNumber surfaceScale;
  readonly attribute SVGAnimatedNumber specularConstant;
  readonly attribute SVGAnimatedNumber specularExponent;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feSpecularLighting' element.

readonly SVGAnimatedNumber surfaceScale

Corresponds to attribute surfaceScale on the given 'feSpecularLighting' element.

readonly SVGAnimatedNumber specularConstant

Corresponds to attribute specularConstant on the given 'feSpecularLighting' element.

readonly SVGAnimatedNumber specularExponent

Corresponds to attribute specularExponent on the given 'feSpecularLighting' element.

Interface SVGFETileElement

The SVGFETileElement interface corresponds to the 'feTile' element.

IDL Definition

interface SVGFETileElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  readonly attribute SVGAnimatedString in1;
};

Attributes

readonly SVGAnimatedString in1

Corresponds to attribute in on the given 'feTile' element.

Interface SVGFETurbulenceElement

The SVGFETurbulenceElement interface corresponds to the 'feTurbulence' element.

IDL Definition

interface SVGFETurbulenceElement : 
                SVGElement,
                SVGFilterPrimitiveStandardAttributes { 

  // Turbulence Types
  const unsigned short SVG_TURBULENCE_TYPE_UNKNOWN      = 0;
  const unsigned short SVG_TURBULENCE_TYPE_FRACTALNOISE = 1;
  const unsigned short SVG_TURBULENCE_TYPE_TURBULENCE   = 2;
  // Stitch Options
  const unsigned short SVG_STITCHTYPE_UNKNOWN  = 0;
  const unsigned short SVG_STITCHTYPE_STITCH   = 1;
  const unsigned short SVG_STITCHTYPE_NOSTITCH = 2;

  readonly attribute SVGAnimatedNumber      baseFrequencyX;
  readonly attribute SVGAnimatedNumber      baseFrequencyY;
  readonly attribute SVGAnimatedInteger     numOctaves;
  readonly attribute SVGAnimatedNumber      seed;
  readonly attribute SVGAnimatedEnumeration stitchTiles;
  readonly attribute SVGAnimatedEnumeration type;
};

Definition group Turbulence Types

Defined constants

SVG_TURBULENCE_TYPE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_TURBULENCE_TYPE_FRACTALNOISE		Corresponds to value fractalNoise.
SVG_TURBULENCE_TYPE_TURBULENCE		Corresponds to value turbulence.

Definition group Stitch Options

Defined constants

SVG_STITCHTYPE_UNKNOWN		The type is not one of predefined types. It is invalid to attempt to define a new value of this type or to attempt to switch an existing value to this type.
SVG_STITCHTYPE_STITCH		Corresponds to value stitch.
SVG_STITCHTYPE_NOSTITCH		Corresponds to value noStitch.

Attributes

readonly SVGAnimatedNumber baseFrequencyX

Corresponds to attribute baseFrequencyX on the given 'feTurbulence' element.

readonly SVGAnimatedNumber baseFrequencyY

Corresponds to attribute baseFrequencyY on the given 'feTurbulence' element.

readonly SVGAnimatedInteger numOctaves

Corresponds to attribute numOctaves on the given 'feTurbulence' element.

readonly SVGAnimatedNumber seed

Corresponds to attribute seed on the given 'feTurbulence' element.

readonly SVGAnimatedEnumeration stitchTiles

Corresponds to attribute stitchTiles on the given 'feTurbulence' element. Takes one of the Stitching Options.

readonly SVGAnimatedEnumeration type

Corresponds to attribute type on the given 'feTurbulence' element. Takes one of the Turbulence Types.