Thread: [Lcms-user] cmsFLAGS_BLACKPOINTCOMPENSATION
An ICC-based CMM for color management
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From: Carles L. <ca...@ci...> - 2006-07-13 12:34:51
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Hello all I'm having some trouble with this flag (or I'm not understanding how to use it) Tell me if I'm wrong but I think that Black Point Compensation is an adaptation to the Relative Colorimetric intent that tries to map the black point of the source profile into the black point of the destination profile. My problem is that i don't see any difference on my results. I've tried many profiles (rgb, cmyk, grayscale... ) and I get allways the same black. Debugging LCMS code I've found that the detection of black points is allways returning X=0.0, Y=0.0, Z=0.0 (L=0, a=0, b=0). I've not activated the HONOR_BLACK_POINT_TAG flag Any suggestion ? thanks Carles Llopis RIP Software Engineer CIBERCAT, S.L. Barcelona, Spain |
From: <ma...@li...> - 2006-07-13 14:35:20
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Hi, You are right, BPC accommodates dynamic range. It makes sense only on relative colorimetric. To check it, try any CMYK profile like SWOP (US Web coated SWOP) or Euroscale, both have nonzero black points. It is quite evident on going from SWOP to sRGB, for example. I don't recommend using HONOR_BLACK_POINT_TAG because most profiles have bogus values on such tag. Saludos Marti. Quoting Carles Llopis <ca...@ci...>: > > Hello all > > I'm having some trouble with this flag (or I'm not understanding how to use > it) > Tell me if I'm wrong but I think that Black Point Compensation is an > adaptation to the Relative Colorimetric intent that tries to map the black > point of the source profile into the black point of the destination profile. > My problem is that i don't see any difference on my results. I've tried many > profiles (rgb, cmyk, grayscale... ) and I get allways the same black. > Debugging LCMS code I've found that the detection of black points is allways > returning X=0.0, Y=0.0, Z=0.0 (L=0, a=0, b=0). > > I've not activated the HONOR_BLACK_POINT_TAG flag > > > Any suggestion ? > > > thanks > > > Carles Llopis > RIP Software Engineer > CIBERCAT, S.L. > Barcelona, Spain > > > > |