440736 - Better CMYK to RGB conversion

Status: RESOLVED DUPLICATE of bug 500501

(Core :: Graphics: ImageLib, defect)

Description

[Uri Bernstein]

In bug 44781, CMYK support was implemented using a simple, linear, transformation from CMYK to RGB.
As bug 44781 comment 58 notes, the results when using such transforms are far from optimal, and indeed the colors of CMYK JPGs are significantly distorted when viewed in Firefox, as compared to Safari (or Photoshop).

According to the comments in that bug, most good transform algorithms are patent-protected. However, I'm reporting this issue in hope that an open algorithm can be found (or designed from scratch), that would yield better results than what we currently have.

This was brought to my attention by rc_p on the mozilla.org.il forums: http://mozilla.org.il/board/viewtopic.php?f=9&t=6388 (in Hebrew).

Comment 1

[Alfred Kayser]

As described in bug 44781, better conversion can be achieved by using lcms. The use of lcms can be easily turned on by a config parameter. So, instead of introducing a new conversion just use lcms for this.