Those are two enhancement to gimp. colormetric.patch: Revised the idea of color distance based on a paper by Thiadmer Riemersma (http://www.compuphase.com/cmetric.htm). Now RGB->INDEXED does not map dark colors to blue or light grays to yellow. riemersmadither.patch: Created a new dither option based on a paper by Thiadmer Riemersma (http://www.compuphase.com/riemer.htm). This algorithm combines the advantages of ordered dither and error diffusion dither.
Created attachment 35297 [details, diff] patch for the ebuild
Created attachment 35298 [details, diff] colormetric patch
Created attachment 35299 [details, diff] new dither patch
this changes the behaviour of certain functionality right ? I'm not sure that is a good thing to do by default. What is the upstream take on this ?
The colormetric patch simply updates the formula used in comparison of two rgb colors (adding one more variable) without changes to the main algorithm, so I consider it as a bugfix. The other patch simply adds a new feature, no changes to the rest of the code. I cannot submit this patch directly to gimp manteiners because they accept patches only for the latest version (2.x), currently I'm working on the patch for that release.
I discussed with the upstream gimp maintainers, they would like to see these patches proposed in their bugzilla (http://bugzilla.gnome.org/enter_bug.cgi?product=GIMP) or on their mailinglist. The Gentoo devs cannot really judge these patches for their pros/cons like they can, so without their go-ahead I'm not confident we should put this in. If you have filed these patches please add the upstream buglinks to this report.
submitted to upstream as bug #147481
