Manipulating Images with the GIMP

GIMP Basics

To use the GIMP, you will need to know some of the basics. From a shell prompt, you start the GIMP using the command gimp. Start the GIMP from the desktop panel by choosing Main Menu => Graphics => The GIMP.

Figure 10-8 shows a typical GIMP session in action.

Loading a File

To load an existing file, click on File => Open. You will see the Load Image dialog, as shown in Figure 10-9.

The Load Image dialog displays your working directory — the directory you were in when the GIMP was launched. You can navigate up and down the file system tree by double-clicking on the Directories list on the left, then selecting a file to open from the Files list on the right.

File name completion is supported by the GIMP. If you type the first letter (or more) of a file name into the Selection field and press the [Tab] key, the view will change to only those subdirectories and/or files beginning with that letter or letters.

The file you select will appear in the Selection field near the bottom of the dialog. A thumbnail preview will be displayed on the dialog; alternatively, you will see a Generate Preview button. If you want to see a thumbnail of the image, click on the Generate Preview button.

Once you have selected a file, click on the OK button to open it. You can also double-click on a file name to open it.

Saving a File

To save an image file, right click on the image and choose File => Save (or Save as). You will see the Save Image dialog if you choose Save as or if you choose Save and the file has not been saved before.

The Save Image dialog looks almost exactly like the Load Image dialog and navigation of the file system tree and choosing files works in the same way.

When you are saving an image, you will need to choose an image format. The GIMP supports a wide variety of image formats, including .gif, .png, .jpg, and .bmp.

GIMP Options

Like many applications, the GIMP provides more than one method to accomplish tasks. The easiest way to work with images is to right-click the image, which will display a set of menus containing most of the GIMP's many capabilities, including image sizing, rotation, and filter application.

For example, imagine you have a picture that you would like to modify to make it look as if it were clipped from a newspaper. To do this, right-click on the image and select Filters => Distorts => Newsprint.... Select the quantity of lines per inch using the sliders. When you reach a desired quantity and are ready to render the image, click OK. The GIMP will then render the image with the new effect applied. Figure 10-10 shows an example of an image after the Newsprint filter has been applied:

The Toolbox also has several easily accessible functions. Using the Toolbox, you can add text to images, erase regions of an image, or even fill selected regions with the color of your choice.

For example, if you wish to add text to a file, select the button and click on your image. This will load the Text Tool dialog box, where you can choose a font and type some text in the provided text box. Click OK and your text will be displayed in as a floating section on the image. You can then move the text to the position you wish using the Move Layers tool. Figure 10-11 shows our photo with exciting new text:

As you can see, the GIMP is a powerful imaging tool, and it takes some time to master all of the functions. Try exploring some of the options yourself. If you make a mistake, do not worry. You can always undo your mistakes by right-clicking on the image and choosing Edit => Undo.