[Openicc] colord Printing Plans GhostScript

[Michael Vrhel]

Gerhard,

You are correct. Doing what you describe is not easy and is fraught with 
problems.   Hence it only occurs when someone has been careful to specify to 
ghostscript the same profile to use for the DefaultCMYK input space as is 
used for the CMYK printer that you are going to.  For this simple case, the 
profiles are identical and that is easy to detect through proper hashing 
methods.  The data is then passed along unmolested.   In a situation where 
someone has some funky CSA in a PS file and if it is colorimetrically 
equivalent to a device profile, that is not going to be detected and it will 
go through the mapping.  Hopefully if will be close to identity and there 
will not be any issues in those situations but we all know how that can turn 
out.

Michael

-----Original Message----- 
From: Gerhard Fuernkranz
Sent: Tuesday, March 01, 2011 1:13 PM
To: openicc at lists.freedesktop.org
Subject: Re: [Openicc] colord Printing Plans GhostScript

Am 01.03.2011 07:09, schrieb Michael Vrhel:
> As far as "turning off" transformations for DeviceRGB or DeviceCMYK,
> that will occur in cases where the source and destination profiles are
> the same.

Michael, I'm wondering, how do you determine whether two profiles are
"the same"? Seems not to be easy. Do you sample the whole color space
gamut of both profiles and check for colorimetric differences? Is for
instance an internal ICC profile created from a CSA describing SWOP
color space considered "the same" as USWebCoatedSWOP.icc, if they happen
to match colorimetrically? Or another example, are two RGB profiles "the
same", if the the have the same primaries and also TRC curves with the
same shape, but with a different representation of the TRC in the
profile (e.g. gamma value, versus 1D LUT representing the same curve)?

Regards,
Gerhard

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