What's In A GIF

 (main page)

These pages explain down to the bit level what's inside a GIF, and are offered in the hope they will be useful to programmers using GIFLIB.

The explanation is in three parts:

  1. Bits and Bytes - first we look at the file format that makes up a GIF file
  2. LZW Image Data - a closer look at how image data is compressed within a GIF file
  3. Transparency and Animation - how some of the more advanced features of GIF files work

Due credit: much of this material was written by one Mike Flickinger in 2005, though it has been significantly revised and expanded for GIFLIB. The illustrations are all his.

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