Re: [Lcms-user] Apply profile with PCS = cmsSigXYZData, Color Space = cmsSigGrayData

[Martí M. <mar...@li...>]

Hi,

I just C&P from testbed, sorry.

A portable function should be like this:

static
cmsHPROFILE Create_Gray22(void)
{
     cmsHPROFILE hProfile;
     cmsToneCurve* Curve = cmsBuildGamma(0, 2.2);
     if (Curve == NULL) return NULL;

     hProfile = cmsCreateGrayProfileTHR(0, cmsD50_xyY(), Curve);
     cmsFreeToneCurve(Curve);

     return hProfile;
}

Regards
Marti


>
> On 20/02/2017 17:33, Aaron Boxer wrote:
>> Thanks, Marti. Is the white point and transfer function not already 
>> specified in the profile? Pardon my ignorance,
>> not that familiar with colour transforms.
>>
>> On Mon, Feb 20, 2017 at 11:28 AM, Martí Maria 
>> <mar...@li... <mailto:mar...@li...>> wrote:
>>
>>
>>     Hi,
>>
>>     You need to specify white point and transfer function to
>>     cmsCreateGrayProfile(), see manual page 28
>>
>>     Regards
>>
>>     Marti
>>
>>     On 20/02/2017 7:04, Aaron Boxer wrote:
>>>     Hello,
>>>
>>>     I have a jpeg 2000 file with an ICC profile.
>>>
>>>     PCS is cmsSigXYZData and color space is cmsSigGrayData.
>>>
>>>     The file can be found here:
>>>     https://github.com/GrokImageCompression/grok/issues/38
>>>     <https://github.com/GrokImageCompression/grok/issues/38>
>>>
>>>     I am working on a library that decodes the jpeg 2000 file and
>>>     applies the ICC profile, using LCMS.
>>>
>>>     Currently, I have this code:
>>>
>>>      in_type = TYPE_GRAY_8;
>>>      out_type = TYPE_RGB_8;
>>>      out_prof = cmsCreate_sRGBProfile();
>>>
>>>     and I can create the transform and apply the ICC profile, but
>>>     the output is an RGB file.
>>>     What I would like is to output a grayscale file.
>>>
>>>     So, if I instead call
>>>
>>>     out_prof = cmsCreateGrayProfile(NULL,NULL);
>>>
>>>     then cmsCreateTransform  returns NULL and I can't apply the profile.
>>>
>>>
>>>     What is the best way of creating a transform for this kind of
>>>     grayscale image ?
>>>
>>>     Thanks so much,
>>>     Aaron
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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