[argyllcms] Re: cctiff intent question
- From: Martin Lederhilger <martin.lederhilger@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 04 Apr 2014 14:07:16 +0200
Am Freitag, 4. April 2014, 16:35:49 schrieb Graeme Gill:
> 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.
Hi,
thank you for your answer.
Just to clarify that I have understood correctly: The first intent is for
converting from sRGB to PCS, and the second intent is for converting from PCS
to ISOcoated. Is that correct?
Thank you,
Martin
>
> 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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