Hi That's not a bug, that's a feature. :-)
Some (broken) profiles does not map pure white to pure white, and this may cause "scum dot" which is small, disperse dots on the printout. Please note that ICC spec *requires* white to be mapped on white. Lcms silently fixes those broken profiles. Unfortunately, that may affect to your case, too. Just use cmsFLAGS_NOWHITEONWHITEFIXUP on the flags field of cmsCreateMultiprofileTransform, and make sure to upgrade to 1.16. Regards Marti. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Boudewijn Rempt Sent: Thursday, January 11, 2007 9:39 AM To: lcms-user@lists.sourceforge.net Cc: Boemann, Casper Subject: [Lcms-user] Problem with modifying the lightness of white pixels with lcms? Hi, Casper, one of the Krita hackers asked me to ask the about following: --- After having used lcms to do some lightness transformation using the following code I've come across a problem. My code tries to convert from a working colorspace to lab and back. But whil in lab it modifies the L* channel with the use of a transfer table. The trouble is that white pixels are not touched. Even if I set the transform / gamme table to all zero the white pixels remain white. Am I doing something wrong or is there a bug in lcms: LPGAMMATABLE transferFunctions[3]; transferFunctions[0] = cmsBuildGamma(256, 1.0); transferFunctions[1] = cmsBuildGamma(256, 1.0); transferFunctions[2] = cmsBuildGamma(256, 1.0); for(int i =0; i < 256; i++) transferFunctions[0]->GammaTable[i] = transferValues[i]; profiles[1] = cmsCreateLinearizationDeviceLink(icSigLabData, transferFunctions); cmsSetDeviceClass(profiles[1], icSigAbstractClass); profiles[0] = m_profile->profile(); profiles[2] = m_profile->profile(); transform = cmsCreateMultiprofileTransform(adj->profiles, 3, m_cmType, m_cmType, INTENT_PERCEPTUAL, 0); cmsDoTransform(transform, src, dst, nPixels); --- Any idea? -- Boudewijn Rempt http://www.valdyas.org/fading/index.cgi ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
