Re: [Lcms-user] Serializing CIELab to buffer

[Aaron B. <bo...@gm...>]

Alright, I now get it : these are the range and offset values for the L,a
and b coordinates in Lab space;
the first block sets the values for Lab space with default illuminant D50.
The second block
is for a non-default Lab space (Jab space, for example ?)

On Fri, Feb 9, 2018 at 9:10 AM, Aaron Boxer <bo...@gm...> wrote:

> Thanks, Noel, I will do that.
>
> Another question: there seems to be two ways of defining the CIELab
> profile, a default profile
> and also a custom profile determined by the 7 values stored in the JP2
> file.
>
> The logic is:
>
>         int row[9];
>         if(default_type == 0x44454600) { /* DEF : default */
>             rl = 100;
>             ra = 170;
>             rb = 200;
>             ol = 0;
>             oa = pow(2, prec1 - 1);
>             ob = pow(2, prec2 - 2) +  pow(2, prec2 - 3);
>         } else {
>             rl = row[2];
>             ra = row[4];
>             rb = row[6];
>             ol = row[3];
>             oa = row[5];
>             ob = row[7];
>         }
>
> For the custom profile, can I get LCMS to save this into a single buffer?
>
> Thanks a lot,
> Aaron
>
>
>
> On Fri, Feb 9, 2018 at 8:43 AM, Noel Carboni <NCarboni@prodigitalsoftware.
> com> wrote:
>
>> Look into the cmsSaveProfile.... functions.
>>
>>
>>
>> By the way (for Marti) there's a typo in the documentation for
>> cmsSaveProfileToMem; "guareanteed" should be "guaranteed".
>>
>>
>>
>> -Noel
>>
>>
>>
>> *From:* Aaron Boxer [mailto:bo...@gm...]
>> *Sent:* Fri, February 9, 2018 8:33 AM
>> *To:* lcm...@li...
>> *Subject:* [Lcms-user] Serializing CIELab to buffer
>>
>>
>>
>> Hello Everyone,
>>
>> I have a JPEG 2000 image with a stored CIELab color profile.
>>
>> This profile is determined by 7 32 bit values.
>>
>> My code currently uses LCMS to apply the profile to the image before
>> decoding to TIFF.
>>
>> I would prefer to store this color profile in the TIFF image.
>>
>> I can do that if I can serialize the profile into a buffer of bytes.
>>
>> I am using LCMS to apply the CIELab as follows:
>>
>>         cmsHPROFILE in = cmsCreateLab4Profile(nullptr);
>>         cmsHPROFILE out = cmsCreate_sRGBProfile();
>>         cmsHTRANSFORM transform =
>>             cmsCreateTransform(in, TYPE_Lab_DBL, out, TYPE_RGB_16,
>> INTENT_PERCEPTUAL, 0);
>>
>>
>>
>> and then applying the transform to each pixel.
>>
>> Is there a way of serializing this profile to a memory buffer, so that I
>> can store it in the TIFF file?
>>
>>
>>
>> Thanks so much,
>>
>> Aaron
>>
>>
>>
>>
>>
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>