GNOME Bugzilla – Bug 626944
Decompose/Recompose LAB use wrong colorspace/gamma
Last modified: 2015-05-02 17:53:44 UTC
As already discussed on the mailing list, the Decompose/Recompose plug-in ignores gamma and uses a wrong conversion matrix: PAL/SECAM RGB instead of sRGB. I am posting a patch, but that patch does *not* work with current git master, rather it needs the "libgimpcolor-new-L-a-b-and-L-C-H-conversions-v3" patch posted at https://bugzilla.gnome.org/show_bug.cgi?id=325564 So basically I'm posting this here as a smaller testbed for the new libgimp routines.
Created attachment 167878 [details] [review] LAB decompose/recompose w/ new libgimp L*a*b conversions
A reminder that the decompose/compose plug-ins don't live up to their promise anymore is certainly a good thing. However, in contrast to the 'color' layer modes recently under discussion on the mailing list, these two plug-ins should deliver what they promise with scientific rigor -- that is, they need to be fully color-managed and pay attention to the current color profile. Besides, backwards compatibility suggests to leave the old wrong functions untouched and add new correct ones instead. Another option to test-drive the new libgimp functions would be create a new plug-in which provides correct conversions under the explicit precondition that the working color space is sRGB. This plug-in surely won't make it into core GIMP, though. Everything IMHO, as always
Review of attachment 167878 [details] [review]: The plug-in should be changed to use the pixel format conversions from babl.
compose and decompose have been ported to gegl/babl, so this bug is completely out of date. If there are still issues with the new code, please file a new bug.