Thread: [Lcms-user] Gamut checks when soft proofing from a linear gamma color space
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From: Elle S. <ell...@ni...> - 2015-03-26 17:52:27
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When editing a linear gamma image, the LCMS soft proofing gamut checks aren't correct. I checked in GIMP and also at the command line using this command: "tificc -i source_profile.icc -t1 -w32 -p dest_profile.icc -g -m1 image.tif image_with_gamutchecks.tif". and the gamut checks were pretty much the same both ways. Here are screenshots that illustrate the problem: http://ninedegreesbelow.com/bug-reports/lcms/soft-proofing-gamut-check-linear-gamma-profile-to-srgb.jpg In the screenshots, the gamut checks are black. The actual image is blue: 1. When soft proofing from the linear gamma working space to the regular sRGB color space, the entire image background shows as out of gamut. Only the light blue fish show as in gamut. 2. After converting the image from the original linear gamma working space to a perceptually uniform version of the same working space, most of the image shows as "in gamut", but the only change was converting to a perceptually uniform version of the original linear gamma RGB color space. So the colors were the same in both images, only the RGB encoding changed. I will guess that the LCMS gamut check code is designed to work with perceptually uniform color spaces, yes? Can the precision be increased so gamut checks can also work with linear gamma color spaces? Best, Elle |
From: <mar...@li...> - 2015-03-28 14:33:05
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Hi Elle. Thanks for reporting. Now this is in the TODO list for next release Regards Marti Quoting Elle Stone <ell...@ni...>: > When editing a linear gamma image, the LCMS soft proofing gamut checks > aren't correct. I checked in GIMP and also at the command line using > this command: "tificc -i source_profile.icc -t1 -w32 -p dest_profile.icc > -g -m1 image.tif image_with_gamutchecks.tif". and the gamut checks were > pretty much the same both ways. > > Here are screenshots that illustrate the problem: > > http://ninedegreesbelow.com/bug-reports/lcms/soft-proofing-gamut-check-linear-gamma-profile-to-srgb.jpg > > In the screenshots, the gamut checks are black. The actual image is blue: > > 1. When soft proofing from the linear gamma working space to the regular > sRGB color space, the entire image background shows as out of gamut. > Only the light blue fish show as in gamut. > > 2. After converting the image from the original linear gamma working > space to a perceptually uniform version of the same working space, most > of the image shows as "in gamut", but the only change was converting to > a perceptually uniform version of the original linear gamma RGB color > space. So the colors were the same in both images, only the RGB encoding > changed. > > I will guess that the LCMS gamut check code is designed to work with > perceptually uniform color spaces, yes? Can the precision be increased > so gamut checks can also work with linear gamma color spaces? > > Best, > Elle > > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming The Go Parallel Website, > sponsored > by Intel and developed in partnership with Slashdot Media, is your > hub for all > things parallel software development, from weekly thought leadership blogs to > news, videos, case studies, tutorials and more. Take a look and join the > conversation now. http://goparallel.sourceforge.net/ > _______________________________________________ > Lcms-user mailing list > Lcm...@li... > https://lists.sourceforge.net/lists/listinfo/lcms-user |
From: Elle S. <ell...@ni...> - 2015-03-28 15:20:57
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On 03/28/2015 10:32 AM, mar...@li... wrote: > > Hi Elle. > > Thanks for reporting. Now this is in the TODO list for next release > Regards > Marti Hi Marti, and thanks! Elle > > Quoting Elle Stone <ell...@ni...>: > >> When editing a linear gamma image, the LCMS soft proofing gamut checks >> aren't correct. I checked in GIMP and also at the command line using >> this command: "tificc -i source_profile.icc -t1 -w32 -p dest_profile.icc >> -g -m1 image.tif image_with_gamutchecks.tif". and the gamut checks were >> pretty much the same both ways. >> >> Here are screenshots that illustrate the problem: >> >> http://ninedegreesbelow.com/bug-reports/lcms/soft-proofing-gamut-check-linear-gamma-profile-to-srgb.jpg >> >> >> In the screenshots, the gamut checks are black. The actual image is blue: >> >> 1. When soft proofing from the linear gamma working space to the regular >> sRGB color space, the entire image background shows as out of gamut. >> Only the light blue fish show as in gamut. >> >> 2. After converting the image from the original linear gamma working >> space to a perceptually uniform version of the same working space, most >> of the image shows as "in gamut", but the only change was converting to >> a perceptually uniform version of the original linear gamma RGB color >> space. So the colors were the same in both images, only the RGB encoding >> changed. >> >> I will guess that the LCMS gamut check code is designed to work with >> perceptually uniform color spaces, yes? Can the precision be increased >> so gamut checks can also work with linear gamma color spaces? >> >> Best, >> Elle >> >> ------------------------------------------------------------------------------ >> >> Dive into the World of Parallel Programming The Go Parallel Website, >> sponsored >> by Intel and developed in partnership with Slashdot Media, is your hub >> for all >> things parallel software development, from weekly thought leadership >> blogs to >> news, videos, case studies, tutorials and more. Take a look and join the >> conversation now. http://goparallel.sourceforge.net/ >> _______________________________________________ >> Lcms-user mailing list >> Lcm...@li... >> https://lists.sourceforge.net/lists/listinfo/lcms-user > > > |