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ULEAD GIF ANIMATOR USER GUIDE
Appendix: GIF color palettes
In a GIF animation file, all images in each frame together contain an index table that defines
the number of colors within the frame and exactly which colors each index represents. Every
color in the maximum 256-color ‘spectrum’ has its own unique identification, which is stored
in the image’s color index (the color palette). In GIF files, each color in the index needs 3 or 4
bytes of data to define it (depending on how it was originally stored). Therefore, an image with
a 256-color palette could have a color index of up to 1024 bytes in size.
There are two kinds of palettes for animated GIFs: a Global Palette, which defines the colors
of all images within the frames in the animation use by default; and a Local Palette, which is
unique to each frame in the file. When a new frame is inserted into a GIF animation, you can
select to use either its Local Palette or the Global Palette.
When you are ready to insert frames into your animation file, you should decide how you want
to manage your color palettes. If every frame contains virtually identical colors, then there is
no reason to fatten your animation file with redundant information by including a Local Palette
in each frame. However, if new frames have colors not found in the Global Palette, you might
want to choose a Local Palette instead.
It’s not always recommended that you use the Global Palette. Reducing the animation’s file
size is not as important as maintaining the quality of your work, but it should be a serious
consideration. The best time to use a Local Palette instead of a Global Palette is when the
frame being inserted is drastically different from the existing frames.
