Thread: [Lcms-user] Re: How can I .....
An ICC-based CMM for color management
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From: <ma...@li...> - 2001-06-09 14:43:56
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Ciao Bernardo, > What can I do to obtain in the OutputBuffer the Lab value? Just use lcmslabi.icm (present on distribution packages) as output = profile. For converting from/to floating point, you have the routines in = lcmsapi.txt, here I reproduce... ---------------------------------- // Convert L to double double L2float(WORD v) { Fixed32 fix32; fix32 =3D (Fixed32) v; return (double) fix32 / 652.800; } // the a/b part double ab2float(WORD v) { Fixed32 fix32; fix32 =3D (Fixed32) v; return ((double) fix32/256.0)-128.0; } --------------------------------------- Then, your code will be something like... (please note I'm using 16 bits = Lab, TYPE_Lab_16) | WORD Output[3] | hOutputProfile =3D cmsOpenProfileFormFile("lcmslabi.icm", "r"); | cmsHTRANSFORM hTransform =3D cmsCreateTrasform (hInputProfile, = TYPE_RGB_8, | = hOutputProfile, TYPE_Lab_16, | = INTENT_PERCEPTUAL, 0) = | ... =20 Translating 1 pixel=20 | cmsDoTransform(hTransform, InputBuffer, OutputBuffer, 1) | L =3D L2Float(Output[0]); | a =3D ab2Float(Output[1]); | b =3D ab2Float(Output[2]); =20 Hope this helps. Mart=ED Maria The little cms project http://www.littlecms.com ma...@li... ----- Original Message -----=20 From: "Bernardo Pucci" <cyb...@ti...> To: <in...@li...> Sent: Saturday, June 09, 2001 3:46 PM Subject: How can I ..... > Hi littlecms stuff, > I'm an Italian student and I use the littlecms engine to obtain color = space > conversion. > No problem happen If I trasform an image (RGB buffer) between 2 icc > profiles (INPUT and DISPLAY), but I don't understand how I can obtain = a Lab > buffer from an RGB buffer with the use of an INPUT profile only. > I must have Lab value for metrics size and I use an INPUT (digital > fotocamera) icc profile with color space RGB and connection space Lab. > The problem occurs (segmentation fault) when trasform is create: >=20 > cmsHTRANSFORM hTransform =3D cmsCreate Trasform (hInputProfile, = TYPE_RGB_8, > NULL, TYPE_Lab_8, >=20 > INTENT_PERCEPTUAL, 0); > What can I do to obtain in the OutputBuffer the Lab value? >=20 > I have define: > unsigned char InputBuffer for RGB value > float OutputBuffer for Lab value. >=20 > In hoping for a reply thanks > Pucci Bernardo >=20 >=20 >=20 |
From: Trigonix inc. <in...@tr...> - 2001-06-11 13:11:05
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Hi, how can i use the IT8 to generate an ICM profile to calibrate a scanner that I`m working on. Thanks. Adil. |
From: <ma...@li...> - 2001-06-11 13:26:50
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Hi, Building profiles is still a pending subject for little cms, however, KWLee has a free program that does just what you ask for: http://www.littlecms.com/iphoto/download.htm The profiles generated by this tool has been tested and works fine under lcms. Martí. ----- Original Message ----- From: "Trigonix inc." <in...@tr...> To: "Martí Maria" <ma...@li...> Cc: <lcm...@li...> Sent: Monday, June 11, 2001 3:08 PM Subject: [Lcms-user] Scanner calibration > > > > > Hi, > how can i use the IT8 to generate an ICM profile to calibrate a scanner > that I`m working on. > Thanks. > Adil. > > > _______________________________________________ > Lcms-user mailing list > Lcm...@li... > http://lists.sourceforge.net/lists/listinfo/lcms-user > > |
From: <ma...@li...> - 2001-06-11 15:20:01
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Hi, Let me see if I understand the problem.... You have an IT/8 target, then you scan this target and got a image in RGB. Ok right now. Then, the IT/8 sheet has Lab values for patches ... and you want to generate a icc profile that characterizes the translation from your RGB values to Lab values. Is this? So, this is just what profiler is doing. You give to the profiler the RGB scanned image, the IT/8 reference sheet and the profiler resturn to you the icc profile. The full process of obtaining a profile from a set of patches is very complex. I can outline an algorithm for doing so, but there is a lot of math/color science involved... I guess is not worth of the effort required to just build one profile. If you want to use this profile somehow embedded into scanner firmware, you need to know in wich RGB space your scanner is going to work. Assuming sRGB, a transform between the obtained profile and sRGB profile will give to you the corrected RGB values. Martí. ----- Original Message ----- From: "Trigonix inc." <in...@tr...> To: "Martí Maria" <ma...@li...> Sent: Monday, June 11, 2001 3:44 PM Subject: Re: [Lcms-user] Scanner calibration > Hi, > I don`t need a software to do the calibration. > the scanner i à working on is under developement, and we have somme probleme > with colors :). > So i scanned an IT8 target and compare the value (in RGB) a obtained and the > value given with the target. > I know that there is a way to write a program in c++ to generate a profile > (icc) to do some intepolation and to calibrate the scanner but HOW? > > thanks > > > Martí Maria wrote: > > > Hi, > > > > Building profiles is still a pending subject for little cms, > > however, KWLee has a free program that does just > > what you ask for: > > > > http://www.littlecms.com/iphoto/download.htm > > > > The profiles generated by this tool has been tested and works > > fine under lcms. > > > > Martí. > > > > ----- Original Message ----- > > From: "Trigonix inc." <in...@tr...> > > To: "Martí Maria" <ma...@li...> > > Cc: <lcm...@li...> > > Sent: Monday, June 11, 2001 3:08 PM > > Subject: [Lcms-user] Scanner calibration > > > > > > > > > > > > > > > > > Hi, > > > how can i use the IT8 to generate an ICM profile to calibrate a scanner > > > that I`m working on. > > > Thanks. > > > Adil. > > > > > > > > > _______________________________________________ > > > Lcms-user mailing list > > > Lcm...@li... > > > http://lists.sourceforge.net/lists/listinfo/lcms-user > > > > > > > > -- > =============== Certifiée ISO9002 ================ > Trigonix Inc. > 80 rue Queen, bureau 101 > Montreal, QC, CAN H3C 2N5 > Tel: (514) 874-0443 > Fax: (514) 874-0339 > email: in...@tr... > > > > |
From: Karl H. K. <kh...@kh...> - 2001-06-12 01:10:39
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=2E.. and if you really want sourcecode, take a look at http://www.scarse.org - this is a package (for Unix however) to create scanner profiles. It does not use lcms to read or write ICC profiles. Karl Heinz On Mon, Jun 11, 2001 at 05:21:10PM +0200, Mart=ED Maria wrote: > Hi, >=20 > Let me see if I understand the problem.... >=20 > You have an IT/8 target, then you scan this target and > got a image in RGB. Ok right now. Then, the IT/8 sheet > has Lab values for patches ... and you want to > generate a icc profile that characterizes the translation from > your RGB values to Lab values. Is this? So, this is just what > profiler is doing. You give to the profiler the RGB scanned > image, the IT/8 reference sheet and the profiler resturn to you > the icc profile. >=20 > The full process of obtaining a profile from a set of patches is > very complex. I can outline an algorithm for doing so, but > there is a lot of math/color science involved... I guess is not > worth of the effort required to just build one profile. >=20 > If you want to use this profile somehow embedded into scanner > firmware, you need to know in wich RGB space your scanner > is going to work. Assuming sRGB, a transform between > the obtained profile and sRGB profile will give to you the > corrected RGB values. >=20 > Mart=ED. >=20 > ----- Original Message ----- > From: "Trigonix inc." <in...@tr...> > To: "Mart=ED Maria" <ma...@li...> > Sent: Monday, June 11, 2001 3:44 PM > Subject: Re: [Lcms-user] Scanner calibration >=20 >=20 > > Hi, > > I don`t need a software to do the calibration. > > the scanner i =E0 working on is under developement, and we have somme > probleme > > with colors :). > > So i scanned an IT8 target and compare the value (in RGB) a obtained and > the > > value given with the target. > > I know that there is a way to write a program in c++ to generate a prof= ile > > (icc) to do some intepolation and to calibrate the scanner but HOW? > > > > thanks > > > > > > Mart=ED Maria wrote: > > > > > Hi, > > > > > > Building profiles is still a pending subject for little cms, > > > however, KWLee has a free program that does just > > > what you ask for: > > > > > > http://www.littlecms.com/iphoto/download.htm > > > > > > The profiles generated by this tool has been tested and works > > > fine under lcms. > > > > > > Mart=ED. > > > > > > ----- Original Message ----- > > > From: "Trigonix inc." <in...@tr...> > > > To: "Mart=ED Maria" <ma...@li...> > > > Cc: <lcm...@li...> > > > Sent: Monday, June 11, 2001 3:08 PM > > > Subject: [Lcms-user] Scanner calibration > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > how can i use the IT8 to generate an ICM profile to calibrate a > scanner > > > > that I`m working on. > > > > Thanks. > > > > Adil. > > > > > > > > > > > > _______________________________________________ > > > > Lcms-user mailing list > > > > Lcm...@li... > > > > http://lists.sourceforge.net/lists/listinfo/lcms-user > > > > > > > > > > > > -- > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Certifi=E9e ISO9002 =3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > Trigonix Inc. > > 80 rue Queen, bureau 101 > > Montreal, QC, CAN H3C 2N5 > > Tel: (514) 874-0443 > > Fax: (514) 874-0339 > > email: in...@tr... > > > > > > > > >=20 >=20 > _______________________________________________ > Lcms-user mailing list > Lcm...@li... > http://lists.sourceforge.net/lists/listinfo/lcms-user --=20 Karl Heinz Kremer kh...@kh... PGP Key at http://www.freecolormanagement.com/download/khk.asc EPSON Sane Backend: http://www.freecolormanagement.com |