Some GIF images lead to wrong, unexpected results in converted .pdt image tables

Problem

The pdc conversion of some animated GIFs results in incorrect image tables:

Good Example

original animated GIF (10,069 bytes)
1015.goose

converted pdt file (good)

Bad Example

optimised animated GIF (1,018 bytes)
1015.goose.opt

converted pdt file (bad)

Analysis

  • The problematic GIFs are “optimized” for small file size (using one or more of: partial frames, empty frames or various other tricks)
  • You can use gifsicle --optimize to generate such a GIF, but whether or not this file will result in the problem depends on the content of the image and the finer details of how it has been optimized
  • Worth mentioning that gifsicle is not the only source of such optimized GIF images

Workaround

  • use unoptimized GIFs (use gifsicle --unoptimize to convert problematic images)