Color Values
All color values passed to the accelerated rendering functions are packed
pixel values, that will need to be pre-packed into the proper format
required by the current framebuffer mode. In 8 bit color index modes,
this is simply a color index between 0 and 255. In the 15 bits per
pixel and above modes, you will need to pack the color values according
to the RGB pixel format information stored in the GA_modeInfo information
block. The RGB pixel format information specifies the mask size and bit
positions for all red, green, blue and alpha components (alpha is
generally ignored for framebuffer values). These mask should be used by
the application to pack the appropriate RGB color values into a 32-bit
integer to be passed to the appropriate rendering routines.
Currently the alpha component in 15-bit and 32-bits per pixel modes is
unused, and should always be set to 0 for normal 2D rendering
operations, as on some controllers these bits may be significant. For
alpha blended operations, these bits can be used to control the
blending of pixel colors during rendering.
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