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GIF
The Save As GIF dialog has many options. If you\'ve flattened your image, you can save it as an interlaced GIF image, which enables it to be loaded incrementally by some applications (such as Netscape). You\'ve probably seen this on the Web, when the image appears blurry at first but gradually becomes sharper.
You can also set the GIF Comment stored in the GIF file to anything you want, like, \"Made by Karin with Gimp.\" Note that if you want to change the default GIF comment (\"Made with GIMP\"), you\'ll need to edit the GIF plug-in source code.
Note that you\'ll need to convert your image to indexed color (right-click|Image|Indexed) before you can save it as a GIF.
If your image contains layers, you can create a GIF animation. If you want the animation to play only once, uncheck the Loop box; otherwise, it will loop forever. The Default delay between frames where unspecified field is the delay between frames in your animation. The checkboxes in the Default disposal where unspecified section control the following actions:
· Don\'t care and Make frame from cumulative layers have the same effect: The animation starts by displaying the first layer in the GIF image. Subsequent layers are then displayed \"on top of\" each other. This mode is useful when creating, for example, a logo that you\'d like to appear one letter at a time.
· One frame per layer (replace) will use the first layer as the first frame, the second layer as the second frame and so on, just like in a movie. This mode is useful when creating an image of a moving object, such as a spinning globe.
If your GIF image is transparent, the transparency will be retained when you save it. Transparency works in both flat and layered images. Note that GIF does not support semi-transparency; pixels are either 100 percent opaque or 100 percent transparent.
Transparent GIF images will sometimes be displayed incorrectly. This happens in a few older image programs that can\'t handle transparency very well, and you\'ll see a color instead of transparency (for example, Photoshop 2.5 doesn\'t handle transparency). The best you can do is set the image\'s default background color to an appropriate color before saving the GIF.
Kilde:
http://manual.gimp.org/manual/GUM/file_and_save2.html/Rob