I need to make a color conversion including the gamma all in the software, I convert L*a*b* to RGB. One reason is that part of my project is on a system with no VCGT support. The second is that when on a PC (Win or MAC), I would like to have the gamma applied also in software so it can be streamed via VNC to a remote desktop.
I see that when doing a color conversion with Little CMS, the VCGT tag is ignored. I tried to extract the VCGT and write the tone curves to the GAMT tag, but I got an error "Malformed struct in type 'mBA ' for tag 'gamt'". This is the code: cmsToneCurve **gammaCurves = (cmsToneCurve**)cmsReadTag(inProfile, cmsSigVcgtTag); cmsWriteTag(inProfile, cmsSigGamutTag, gammaCurves); VCGT data is read OK, there are all the values. But I am unable to save them as GAMT. Further I tried to save the gamma curves in the TRC tags, which was successful, but the TRC tags are also ignored when doing color conversion with Little CMS. In the system with no VCGT support I create a multi-profile transform (cmsCreateMultiprofileTransform(...)) with three profiles: Lab, my profile with VCGT and the third profile is a Linearization device link with color space from the second and tone curves extracted from the VCGT tag. This multi-profile transform looks that it works good, the final RGB values are a bit shifted. Where should I put the tone curves from the VCGT tag, so Little CMS will apply the the gamma correction in a transformation directly without a multi-profile transformation? And where should I put them, so Windows 7/8 and MAC OS X 10.8 will apply them in software instead of uploading them to a GPU? Thank you. -- Martin Florek ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60134791&iu=/4140/ostg.clktrk _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
