Oh, I see... You profile forces L* to zero but keeps a* and b*,
Right, the interpretation on what something like Lab (0, 10, 20) means, is up to the output profile. Hint: L*=0 does not always map to sRGB=(0,0,0). Try transicc or Photoshop: transicc.exe -i*Lab -o*sRGB LittleCMS ColorSpace conversion calculator - 4.3 [LittleCMS 2.08] Enter values, 'q' to quit L*? 0 a*? 10 b*? 20 R=29.9669 G=-9.1523 B=-48.4744 Here you got a lot of red from L*=0, and this is mathematically correct. Do the math by hand if you are not convinced. Regards Marti Quoting Boudewijn Rempt <b...@valdyas.org>: > Hi, > > Hm... It's much better, but still not perfect... I've attached a > sample profile that should have made the image all-black. > > Boud > > On Tue, 26 May 2015, marti.ma...@littlecms.com wrote: > >> >> >> Hi, >> >> Try "cmsFLAGS_NOWHITEONWHITEFIXUP" >> >> On some optimizations, lcms "fixes" white to be pure white by >> patching the upper node. This is to prevent dispersed dots being >> spread all over the paper when printing. >> >> If that does not work, please send me a sample profile (use >> cmsSaveProfileToFile) and I'll give a try... >> >> Regards >> Marti >> >> >> Quoting Boudewijn Rempt <b...@valdyas.org>: >> >>> Hi, >>> >>> Ten years ago, we implemented a curve-based brightness/contrast filter in >>> Krita using this: >>> >>> https://www.mail-archive.com/lcms-user@lists.sourceforge.net/msg01509.html >>> >>> Now we've got a bug report about it: >>> >>> https://bugs.kde.org/show_bug.cgi?id=347533 >>> >>> If all the values of the curve are 0, we'd expect the output of the filter >>> to be completely black, because there's no lightness anymore, and if all >>> the values are 0xFFFF, we'd expect the output to be totally white. >>> >>> But in fact, in either case a ghost of the image is still visible. I'm not >>> sure what's up, but it's something that happens inside lcms2. I've tried >>> with different intents and conversion flags, but that doesn't seem to >>> matter. >>> >>> Boudewijn >>> >>> ------------------------------------------------------------------------------ >>> One dashboard for servers and applications across Physical-Virtual-Cloud >>> Widest out-of-the-box monitoring support with 50+ applications >>> Performance metrics, stats and reports that give you Actionable Insights >>> Deep dive visibility with transaction tracing using APM Insight. >>> http://ad.doubleclick.net/ddm/clk/290420510;117567292;y >>> _______________________________________________ >>> Lcms-user mailing list >>> Lcms-user@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/lcms-user >> >> ------------------------------------------------------------------------------ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
