Build/find Rust gif codec

[lilith]

Needs:

• Animated gif decode (and encode!) support. Remember that animated gifs can use frame-by-frame deltas in two ways - one, by only including a subset of the global canvas (i.e, left,right offset and smaller width/height for frame), and two, by using transparent pixels.
• GIF87 and 89a support.
• Decent test suite.

Prior art:
https://github.com/pcwalton/rust-media/blob/master/containers/gif.rs
https://github.com/PistonDevelopers/image-gif

image-gif is very promising. We should try wiring it up to Imageflow.

[stonetip]

We never use GIFs and have used 8 or 24-bit PNGs (or SVGs) for a long time now. For the first time in a few years, I actually made an animated GIF the other day (comparing two maps) and despite Photoshop's best optimizations it was 7 Mb! I ended up sending a 784K MPEG instead. What's important to us is photographic and aerial/remote sensing imagery - balancing the best, sharpest images with the smallest file sizes, processed as quickly as possible.

[Charmatzis]

Well done, that's great news for the GIS community!

[shmuelie]

Annoying enough in GIS we are stuck sometimes with GIFs over MPEG (and the like) so imageflow having support for GIF would be great.

[lilith]

Gif read/write is implemented (not animated yet, though)