[argyllcms] Re: cctiff intent question
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 04 Apr 2014 16:35:49 +1100
Martin Lederhilger wrote:
> I have a question regarding the intent switches of cctiff. I want to convert
> with absolute rendering intent, and if I run cctiff with
>
> cctiff -ip sRGB.icm -ia ISOcoated_v2_eci.icc rgb.tif cmyk.tif
>
> then the output image is the same as if I converted with Imagemagick's
> convert, or other tools I have tried. If I run cctiff with
>
> cctiff -ia sRGB.icm -ia ISOcoated_v2_eci.icc rgb.tif cmyk.tif
>
> then the output image is slightly different.
>
> What is the reason why I can specify multiple intent options, and what does
> the second cctiff invocation differently?
Hi,
each intent switch applies to the following profile. So in
the first case you are using the perceptual intent of sRGB.icm and the
absolute intent of ISOcoated_v2_eci.icc.
In the second case you are using absolute intent for both the profiles.
Naturally you end up with a different result, because you asked for
different things. Absolute intent gives you absolute colorimetry,
ie. instrument measurements. Since sRGB has a D65 white point, while
prints using ICC profiles are assumed to be viewed under D50, the
results will look somewhat blue.
Many CMM's, (including LittleCMS by default) follow the ICC's lead and
abuse Absolute intent when it comes to display profiles by disabling it.
To get the same results using ArgyllCMS as these crippled CMM's, simple
use relative colorimetric intent for the display profile.
Graeme Gill.
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