Comment 6 for bug 829213

mikkel: I spent several hours looking into selective optimisation and the internals of libjpeg last night. (There doesn't appear to be any code available)

It'll need some code writing; either based on:

  http://en.wikipedia.org/wiki/Structural_similarity (SSIM metrics)

or specific regions (8x8 pixel granularity) so that the compression/quantisation level is varied per region. This is going to be much longer than I can do in an evening before uploading but is likely to be useful in the long run for allowing greater compression for the CD images (not just wallpapers) without sacrificing perceived quality.

I think for the moment, I'll wait for the 40MB originals from Iain and see what I can do. Of course, with the originals published on this page anyone else is welcome to help with try and help meet the package size target with a better SSIM score.