Using LCMS on hardware

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Using LCMS on hardware
Argentina	2007-03-05 05:34:34
I am currently using LCMS for ICC profile reading and color correction. All is fine. However, for speed purposes, I am now trying to use LCMS just as an ICC profile reader, leaving the color correction to be done on the gfx card with Cg shaders. Therefore, I am looking into LCMS api to see if it can give me the profile data in raw form. Ideally, I would like to call some lcms functions that would tell me how many 2d/3d luts are used, if there is any matrix transform, etc. and then obtain the values of those, so I can use them to feed my shader. However, the docs for the API seem somewhat incomplete. Can anyone roughly point me out to how could I do this? (btw, I will be dealing mainly with RGB->RGB transforms, so I really don't need to handle CMYK and similar transforms). -- Gonzalo Garramuño ggarraadvancedsl.com.ar AMD4400 - ASUS48N-E GeForce7300GT Kubuntu Edgy ------------------------------------------------------------ ------------- 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-userlists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user

Re: Using LCMS on hardware
	2007-03-05 07:02:37
The most obvious way would be to create a transform with lcms in the usual way. You may use proofings multiprofile transforms with all bells and whistles and convert into a device link. This profile should include a 3D LUT to use later, possibly after some conversions, in your cg shader. HDR is only possibly with matrix profiles, best without gamma and outside the above described way. If you consider going open source, the final application could be of general interesst. regards Kai-Uwe Behrmann -- development for color management www.behrmann.name + www.oyranos.org + www.cinepaint.org Am 05.03.07, 08:34 -0300 schrieb gga: > I am currently using LCMS for ICC profile reading and color correction. > All is fine. > > However, for speed purposes, I am now trying to use LCMS just as an ICC > profile reader, leaving the color correction to be done on the gfx card > with Cg shaders. > > Therefore, I am looking into LCMS api to see if it can give me the > profile data in raw form. > Ideally, I would like to call some lcms functions that would tell me how > many 2d/3d luts are used, if there is any matrix transform, etc. and > then obtain the values of those, so I can use them to feed my shader. > > However, the docs for the API seem somewhat incomplete. Can anyone > roughly point me out to how could I do this? (btw, I will be dealing > mainly with RGB->RGB transforms, so I really don't need to handle CMYK > and similar transforms). > > > > -- > Gonzalo GarramuÃ±o > ggarraadvancedsl.com.ar > > AMD4400 - ASUS48N-E > GeForce7300GT > Kubuntu Edgy > ------------------------------------------------------------ ------------- 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-userlists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user

Re: Using LCMS on hardware
Argentina	2007-03-05 11:41:05
Kai-Uwe Behrmann wrote: > The most obvious way would be to create a transform with lcms in the usual > way. You may use proofings multiprofile transforms with all bells and > whistles and convert into a device link. This profile should include a 3D > LUT to use later, possibly after some conversions, in your cg shader. > > HDR is only possibly with matrix profiles, best without gamma and outside > the above described way. Yes, that's one reason for me to wanting to avoid doing lcms transforms and needing the data raw and not wanting lcms to do any processing. Basically, I am hoping lcms' cmsHPROFILE (_lcms_iccprofile_struct ) is keeping its data as float and allowing me to get to that data directly. Or is lcms all 16 bits as soon as data is read (in which case I guess lcms will be pretty much useless to me, and I'll need to it all with CTL)? -- Gonzalo GarramuÃ±o ggarraadvancedsl.com.ar AMD4400 - ASUS48N-E GeForce7300GT Kubuntu Edgy ------------------------------------------------------------ ------------- 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-userlists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user

Re: Using LCMS on hardware
	2007-03-05 13:55:38
Am 05.03.07, 14:41 -0300 schrieb gga: > > Kai-Uwe Behrmann wrote: > > HDR is only possibly with matrix profiles, best without gamma and outside > > the above described way. > Yes, that's one reason for me to wanting to avoid doing lcms transforms > and needing the data raw and not wanting lcms to do any processing. > > Basically, I am hoping lcms' cmsHPROFILE (_lcms_iccprofile_struct ) is > keeping its data as float and allowing me to get to that data directly. > Or is lcms all 16 bits as soon as data is read (in which case I guess > lcms will be pretty much useless to me, and I'll need to it all with CTL)? I am afraid the profile itself contains only 16-bit values in the LUT part of its tables at a extent. The matrixes can be of a signed 15/16-bit type, thus reaching from -32767 to 32767 with 16-bit precision after the point. Still, matrix profiles with gamma 1.0 seems to be a good option. As a hint Greg Ward recommended to use XYZ with a illuminant of type E. Possibly you need some intermediate step to transform from a CLUT colour description or chain as described to a matrix based RGB. The matrix RGB description could remain final or go to XYZ. HDR data should allread be in gamma 1 matrix colour space. For such data a a conversion through the limitted range of curves or LUT may result in clipping. At least a splitting in matrix based HDR and possibly CLUT based LDR transforms should occure. regards Kai-Uwe Behrmann -- development for color management www.behrmann.name + www.oyranos.org + www.cinepaint.org ------------------------------------------------------------ ------------- 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-userlists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user

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