Hi,

> what is the purpouse of the chrm - chromaticityType encoding tag?

That is a pre-v4 tag; (from spec) "The chromaticity tag type provides basic 
chromaticity data and type of phosphors or colorants of a monitor to 
applications and utilities". 

9.2.12 chromaticityTag
Tag signature: 'chrm' (6368726Dh)
Allowed tag type: chromaticity type
The data and type of phosphor/colorant chromaticity set.

Byte position Field Length (bytes) Content Encoded as.
0..3 4 'chrm' (6368726Dh) type signature
4..7 4 reserved, must be set to 0
8..9 2 Number of Device Channels (n) uInt16Number
10..11 2 encoded value of phosphor or colorant type see Table 24
12..19 8 CIE xy coordinate values of channel 1 u16Fixed16Number[2]
20..end (n-1) x 8 CIE xy coordinate values of other n channels (if needed) 
u16Fixed16Number[...]

The [r,g,b,k]XYZ tags holds values after chromatic adaptation, and those are raw 
primaries. 
Now all this stuff is superseded by chromatic adaptation tag. Anyway this tag is merely
 informative, and not used by lcms anymore.

Regards,
Marti Maria
The little cms project
http://www.littlecms.com

----- Original Message ----- 
From: "Kai-Uwe Behrmann" <[EMAIL PROTECTED]>
To: "Lcms Liste" <[EMAIL PROTECTED]>
Sent: Wednesday, August 04, 2004 6:14 PM
Subject: [Lcms-user] chrm tag


Hi,
what is the purpouse of the chrm - chromaticityType encoding tag?
I found it in several profiles created by lcms profilers. Arent the
[r,g,b,k]XYZ tags allready enough?

Marti,
I am unshure with the above tag. I read the number of device channels and
the encoded phosphors as uint16Numbers (2 bytes). As well your entyre tag
has 40 bytes size - for 3 primaries are 36 enough arent they. Please tell
some words about it?

Thanks
Kai-Uwe



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