Hi Elle, I've seen your comparative and it is very good, I guess you have spent a lot of time in creating it. Cool. Most of the questions you raise are answered in my previous mail. See here some additional comments. The issue I'm described is not tied to lcms, you can reproduce it in Argyll as well.
Let's build a devicelink by using Argyll collink. In colling, the default is to keep curves as opposite of lcms linkicc that requires the -l toggle. So, I am using -n on collink to make it behave like linkicc default. collink -n "SRGB_linear.icc" "sRGB Color Space Profile.icm" devlink_sRGB_argyll.icc Then I'm doing same with lcms: linkicc -r3.4 -o devlink_sRGB_lcms2.icc SRGB_linear.icc "sRGB Color Space Profile.icm" Now running cctiff for linear tiff with both devicelinks, ctiff devlink_sRGB_lcms2.icc linear16.tif out_lcms.tif ctiff devlink_sRGB_argyll.icc linear16.tif out_argyll.tif I am obtaining 5 for Argyll and 6 for lcms on the second patch, where it should be 13. Again, this is not a bug of Argyll, neither of lcms. They are just doing what I have asked for. If I let both linkers to use pre/post linearizarion curves, all works fine. It is just that you are pushing to the limits and in some situations defaults does not apply. Finally, a short comment on absolute colorimetric: ICC folks have changed the meaning of absolute colorimetric, so at no wonder you find differences. On lcms2 you have, however, a function to set the observer adaptation state. Setting the state to 0 (fully unadapted) does emulate the old behavior. Setting it to 1 (full adaption) enables the V4 thing. Best regards Marti -----Original Message----- From: Elle Stone [mailto:l.elle.st...@gmail.com] Sent: viernes, 27 de julio de 2012 21:17 To: Boudewijn Rempt Cc: lcms-user@lists.sourceforge.net Subject: Re: [Lcms-user] What does cmsFLAGS_NOOPTIMIZE actually do? I noticed a problem when trying to view regular sRGB and linear gamma sRGB versions of the same image when using Krita 2.4: The linear gamma image was noticeably darker in the shadows. So I did some tests, including converting the linear and regular sRGB images to my monitor profile. The problem turned out to be in the conversion from the image ICC profile to the monitor ICC profile. When converting from the linear gamma image to the monitor profile, the darkest shadows were eye-droppering at about half the value that they should have had. So I created a very simple test image composed of ten blocks: (0,0,0), (1,1,1), (2,2,2), (4,4,4), (8,8,8) and so on, up to (128,128,128), (255,255,255). Then I converted the test image to 16-bits, the corresponding RGB values being 257 times the 8-bit values. Upon using Krita 2.4 to convert the 16-bit linear gamma image to the monitor profile, or to regular sRGB, the second darkest color block ended up with RGB values half of what they should have been. I tried the same test using Cinepaint, cctiff, tificc, showFoto, ImageMagick, GraphicsMagick, and Gimp (at 8 bits only), as well as Krita. I also tried using linear and gamma 1.8 versions of prophoto. cctiff and tificc (using -c 0, which I habitually use and did not think twice about as perhaps being relevant) produced the same values. Cinepaint produced nearly the same values as cctiff and tificc. ALL the other image editing programs cut the darkest shadow values in half. This "cutting in half" of the darkest shadow values is visible and obvious in any image with substantial areas of important shadow detail. I had Cinepaint set in the color management options to use "don't Precalculate" rather than one of the other Cinepaint options (Low Resolution, High Resolution, CMM default). I wish I had realized that particular setting might make a difference, because it would have saved a lot of time and tedious testing. I don't know of any image editing program besides Cinepaint that offers the user the choice to use Low Res, High Res, CMM default, or "Don't Precalculate". I would guess that most or all use something like "CMM default", because I just checked, and Cinepaint, when set to use "CMM default" and "use black point compensation" produces the same halving of the shadow values as all the other image editors. At any rate, at this point every image editor that I tested, other than Cinepaint and the latest Krita 2.6 alpha, produces visibly damaged shadow areas if there is a linear gamma profile involved in an ICC profile conversion. -- http://ninedegreesbelow.com Articles and tutorials on open source digital imaging and photography ---------------------------------------------------------------------------- -- Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
