Hi,
1)In the reply it was mentioned the object measurement data can be
recreated from colorimetric transformation and white point value. I am
not a person having much knowledge about color fundamentals. Could you
please provide me some info as to where I can start to get the necessary
color knowledge that will enable me to port an ICC profile to a WCS
profile(eg:what is color transformation, how is it obtained, how is it
related to object measurement data, what is whitepoint , how is it
obtained etc ).
2) To make my idea of the concept of "transforms on the fly" clearer I
was referring to some documents obtained from the internet. In a
whitepaper at http://www.color.org/ICC_white_paper_24_ICCandWCS.pdf they
have specified the following.
"The idea of run-time color rendering is that the complete color
transformation is constructed at
run-time from various available components, and that the complete
transform is specific to the
imaging conditions required at that time. ICC member companies have
provided various kinds of
run-time color rendering solutions to market as far back as the mid- to
late-1990s. Scitex's Profile
Wizard is one example. Enhanced support for run-time color rendering was
one of the design
objectives in the ICC version 4 revision work, completed in 2001."
Does this excerpt convey that ICCV4 contains "transforms on the fly" ?
regards,
Shameel Abdulla
-----Original Message-----
From: Graeme Gill [mailto:[EMAIL PROTECTED]
Sent: Wednesday, April 04, 2007 7:44 PM
To: Shameel Abdulla (WT01 - Embedded Systems)
Cc: lcms-user@lists.sourceforge.net
Subject: Re: [Lcms-user] is icc profile portable to wcs
[EMAIL PROTECTED] wrote:
> 1) In your reply you specified it is generally possible to recreate
> object measurement data from LUTs in ICC profile. Could you give me
> some pointers on how we can do this?
The base information in an ICC profile is the relative colorimetric
transformation. Given that and the white point, the absolute
colorimetric response of the device is available. In most situations
this exactly corresponds to instrument readings (one case where it does
not, is ICC V4 display profiles, but this issue was discussed on this
list some time ago - check the archives).
The schema for all the WCS profiles and a fair amount of explanatory
detail has been published by Microsoft -
<http://blogs.msdn.com/color_blog/>
is a good place to start to find this stuff. Simply put the two together
:-)
> 2) You said ICC do not create "transforms on the fly". But in ICM 2.0,
> where WCS was not present at all, we could see the API
> "CreateColorTransform". As per my understanding (and your comments)
> this API links the two color transforms and creates one color
> transform out of it which can be used by user application to do the
> color management in one shot.
Yes. But the gamut mapping and inversion of the device behaviour is all
pre-computed in the ICC profile, so the CMM isn't doing anything
interesting.
> 3) Will WCS profiles in any way contain transforms in their LUTs? For
> example let me sight the following tags from WCS cdmp schema.
>
> <xs:complexType name="OneDimensionLutType"> <xs:sequence> <xs:element
> name="Input" type="cdm:FloatList"/> <xs:element name="Output"
> type="cdm:FloatList"/> </xs:sequence> </xs:complexType>
>
> <xs:complexType name="HDRToneResponseCurvesType"> <xs:sequence>
> <xs:element name="RedTRC" type="cdm:OneDimensionLutType"/> <xs:element
> name="GreenTRC" type="cdm:OneDimensionLutType"/> <xs:element
> name="BlueTRC" type="cdm:OneDimensionLutType"/> </xs:sequence>
>
> Like other tags in WCS do these tags contain only object measurement
> data?
So it is claimed. In practice this might be massaged measurement data.
Graeme Gill.
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