[Openicc] color-policy vs. color-infrastructure

[Maria, Marti]

Hi Lars,

>Beware that the proposed test is not sufficient. In-gamut colors may 
>shift in a round-trip test. Such a test depends on the quality of the 
>profile. Most profiles round-trip poorly also for ingamut colors.

Thanks for your clarification. Yes, I discovered that by the hard way. 
I was just omitting implementation details. Current method involves two 
round trips and a ratio/threshold. Taking a ratio of the dE obtained in 
first and second round trip would compensate such variations. They are 
mostly because AToB1 and BToA1 are at different resolutions. But as
said, 
I think geometrical approaches would perform far better.

Regards,
Marti Maria.

------------------------------

Message: 2
Date: Wed, 16 Mar 2005 17:53:25 -0800
From: Lars Borg <borg at adobe.com>
Subject: [Openicc] Re: color-policy vs. color-infrastructure
To: openicc at lists.freedesktop.org
Message-ID: <p06020413be5e92c23e20@[153.32.43.79]>
Content-Type: text/plain; charset=us-ascii; format=flowed

Marti,

Beware that the proposed test is not sufficient. In-gamut colors may 
shift in a round-trip test. Such a test depends on the quality of the 
profile. Most profiles round-trip poorly also for ingamut colors.

Lars


At 10:42 AM +0100 3/16/05, Maria, Marti wrote:
>Hi,
>
>>  Gamut tags are a bit fuzzy at the best of times, and in many
profiles
>>  out there they are simply wrong. As a result, they can't generally
be
>>  relied upon.
>
>Just for the record, it seems Photoshop is not using the gamut tag
>anymore. Lcms is actually using a brain-dead method for inferring gamut
>that works most of times at expense of poor accuracy. The trick is to
>convert values back and forth the colorimetric intent. If color
changes,
>then it is outside gamut.