CGIF is a fast and lightweight GIF encoder that can create GIF animations and
images. Summary of the main features:
- user-defined global or local color-palette with up to 256 colors (limit of the
  GIF format)
- size-optimizations for GIF animations:
  - option to set a pixel to transparent if it has identical color in the
    previous frame (transparency optimization)
  - do encoding just for the rectangular area that differs from the previous
    frame (width/height optimization)
- fast: a GIF with 256 colors and 1024x1024 pixels can be created in below 50 ms
  even on a minimalistic system
- MIT license (permissive)
- different options for GIF animations: static image, N repetitions, infinite
  repetitions
- additional source-code for verifying the encoder after making changes
- user-defined delay time from one frame to the next (can be set independently
  for each frame)
- source-code conforms to the C99 standard