Re: [Lcms-user] General question about CIE Lab and TIFF

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

Thanks, Mark! I will try that, also will post a code snippet of the current
conversion- would rather use lcms
to do the conversion.

On Wed, Aug 21, 2019 at 7:44 PM Mark Allen <m.f...@pl...> wrote:

> I’ve had experience with old image file formats like TIFF but I’m just a
> LittleCMS user. So I don’t know the insides of LittleCMS and I'm not a
> color management expert. But my guesses follow... Keep in mind they're just
> guesses and you're probably better off spending some serious time with the
> LittleCMS documentation.
>
>
> >>Is it possible with lcms to extract the illuminant and Lab range from
> the ICC
> I haven't seen anything regarding a range of values in LittleCMS but I
> don't know every nook and cranny of it. I'd think you'd just have to write
> your own code to check the pixel values. LittleCMS has routines which can
> read ICC tags for you but I'm not knowledgeable enough to know which one(s)
> you want. I'd personally use LittleCMS to set up for a color conversion and
> follow the code in the debugger and watch the part where it figures it out.
> LittleCMS certainly knows how to do it. It may involve this routine:
> _cmsReadMediaWhitePoint but I don't really know the insides of LittleCMS.
> I'd follow it in the debugger once to make sure you get the right result.
> I’d just do what it does. I don’t see a public routine which does it for
> you but I may have missed it.
>
>
> >>And vice-versa, when decompressing custom CIE, can I convert an
> illumanant with Lab range into an ICC profile?
> These create LAB ICC profiles with a white point:
>
> cmsHPROFILE cmsCreateLab2Profile(const cmsCIExyY* WhitePoint);
> cmsHPROFILE cmsCreateLab4Profile(const cmsCIExyY* WhitePoint);
>
> LittleCMS can write that profile to a stream or write it to a file for you
> so you can create an ICC profile. I'm not sure what J2K is after with the
> range part.
>
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