Re: is icc profile portable to wcs

shameel.abdullawipro.com 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.ms
dn.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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 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:graemeargyllcms.com] 
Sent: Wednesday, April 04, 2007 7:44 PM
To: Shameel Abdulla (WT01 - Embedded Systems)
Cc: lcms-userlists.sourceforge.net
Subject: Re: [Lcms-user] is icc profile portable to wcs

shameel.abdullawipro.com 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.ms
dn.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.

------------------------------------------------------------
-------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the
chance to share your
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php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
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