Interlaced GIFs

• A normal GIF file consists of rows of pixels all in sequence, thus the image starts at the top and grows downwards. An interlaced GIF file consists of the same rows of pixels but are reordered so the "full" image appears quickly and then is refined as more rows of pixels arrive.
• Interlacing a GIF images does not save any space or download time.
• It does however give the user the impression of faster loading images.
  • by the end of the first or second pass the user should have a good impression of what the image looks like.
  • To the end of the second pass takes 1/4 of the download time.

Try Guessing What These Images Are Of

First Pass - Every eight row starting at row 0

Second Pass - Add every eight row starting at row 4

Third Pass - Add every fourth row starting at row 2

Fourth Pass - Add every fourth row starting at row 1

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