Hi, > I tried you suggestion and the profile seems fine:
Glad to know :) So, the profile works as expected. For the white point, there is a small utility wtpnt.c that does the trick. For black point, you have to write a small program that calls cmsCIEXYZ XYZ; cmsDetectBlackPoint(hProfile, &XYZ, INTENT_RELATIVE_COLORIMETRIC, 0); Regards, Marti Maria The little cms project http://www.littlecms.com ----- Original Message ----- From: "Auke Nauta" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, December 13, 2004 10:43 PM Subject: [Lcms-user] Re: Get accurate Lab predictions from profile, how? > Hi Marti, > > I tried you suggestion and the profile seems fine: > > These are the result of 9 Lab colours, converted to output profile and > back, using absolute colorimetry: > > Lab in RGB out Back to Lab > 10 0 0 0 17 1 12.6 0.5 -3.6 > 41.1 65.8 38.5 205 2 12 43.5 63.7 37.4 > 85.5 0.3 84.8 252 244 18 85.3 0.2 84.8 > 47.6 -49 28.1 17 156 24 48.2 -49.7 28.5 > 50 0 0 93 110 103 50 -0.3 -0.1 > 31 -0.7 -43.9 23 62 145 30.4 1.4 -49.7 > 39.9 53.4 -32.1 168 25 195 39.8 53.9 -34.2 > 53.1 -34 -20.6 23 176 165 53 -35 -19.7 > 93 1 -8.5 253 255 254 92.7 0.8 -8.7 > > This is nice :) > > However, how do I know, from the profile, what the whitepoint and > blackpoint values really are? > > OK, I just read it in the docs, I will give it a try... > > And, thanks for version 1.14, it is running fine! > > Greetings, > Auke > > > > > > Auke: > > > > This may be due to several reasons. I want to first check the accuracy > > of your profile to know where the problem actually is. So, the way to > > check > > the accuracy of your profile is to use absolute colorimetric. If this > > works, > > then rel. colorimetric is going to work too. But since rel. colorimetric > > implies a white point translation, there is no direct way to measure it. > > > > So, I proposed to use a transform between Lab -> printer profile because > > Lab identity is operating on D50. It is not same as using AdobeRGB as > > input profile. > > > > At that point abs. colorimetric should work. If not, the profile is not > > proper > > and you cannot obtain any further improvement. > > > >>c. I don't *wan*t to use absolute colorimetry as it changes the RGB > >> values > >>too much. For instance white (Lab 100,0,0) is trnaformed to 229,246,255. > >>If I print this, I don't get paper white anymore, yet my paper is > >> becoming > >>even more blue :( > > > > But your unprinted paper is not of Lab=(100, 0, 0) right? Try to measure > > your > > unprinted paper and feed such value to the abs. colorimetric transform. It > > should > > give you a (255, 255, 255) or something really close to that. > > > > Regards, > > Marti. > > > > ------------------------------------------------------- > SF email is sponsored by - The IT Product Guide > Read honest & candid reviews on hundreds of IT Products from real users. > Discover which products truly live up to the hype. Start reading now. > http://productguide.itmanagersjournal.com/ > _______________________________________________ > Lcms-user mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/lcms-user > ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://productguide.itmanagersjournal.com/ _______________________________________________ Lcms-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/lcms-user
