Re: [Lcms-user] Re: Mixing Lab color

[<ma...@li...>]

Hi,

> So for the CMYK to RGB no problem.
> But about the Lab to CMYK what should I use? (here I use INTENT_PERCEPTUAL,
> but I don't know if I should also use RenderIntent)

Is in this transform when render intent does make physicall sense... You have a
Lab color and want to realize it in inks. If the color can be represented, then all
intents are going to be same. But if color cannot be represented, then the intent
does apply. What do you want on these unrepresentable colors? to maintain
saturation? if so, use INTENT_SATURATION. If you want to keep contrast,
then use INTENT_PERCEPTUAL. The profile will remap the color to the
most proper, attending the rules the intent is specifying.

Normally perceptual intents are used, but for pigments perhaps saturation
could be usefull. Anyway it depends on how do you want to handle the
unrealizable colors.

Besides, your Lab->CMYK->RGB is doing a softproof of the printer, you
should see in monitor the *exact* color as printed on paper. Of course assuming
the printer profile is accurate and proper.

Regards,
Marti.

----- Original Message -----
From: "Armindo Da Silva" <tec...@wa...>
To: "Martí Maria" <ma...@li...>
Cc: <Lcm...@li...>
Sent: Tuesday, January 29, 2002 7:23 AM
Subject: [Lcms-user] Re: Mixing Lab color


> Marti,
>
> Concerning the mixing color a question about profile transform :
>
> To convert from Lab to CMYK I do :
>   Lab2CMYKTransform:= cmsCreateTransform(hLabProfile,
>                 TYPE_Lab_16,
>                 hCMYKProfile,
>                 TYPE_CMYK_16,
>                 INTENT_PERCEPTUAL,0);
>
> to convert the mixing result to RGB I do
>
> CMYK2DisplayTransform:= cmsCreateTransform(hCMYKProfile,
>                 TYPE_CMYK_16,
>                 hDisplayProfile,
>                 TYPE_BGR_8,
>                 RenderIntent,0);
>
> where here RenderIntent is a variable that the user can set for using
> Saturation, perceptual....
>
> So for the CMYK to RGB no problem.
> But about the Lab to CMYK what should I use? (here I use INTENT_PERCEPTUAL,
> but I don't know if I should also use RenderIntent)
>
> thanks
>
> Armindo
>
>
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