chrm and image gamma

M
Posted By
maryplanet2003
Apr 8, 2004
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268
Replies
2
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Closed
Hello friends,i’m writing from Italy,
I need a little help, becouse I’ ve to make a very big work, but there is some thing I don’t understand.
I’ve 1000 photo,(3072×2040 pixel) to put on one or more CD in PNG format. Well, the customer ask me to insert chunk:
CHRM Primary chromaticities an white point
GAMA Image Gamma
TEXT Keyword, Version, Data
About text I think is good to insert by FILE-INFO file…, but I don’t know how I Have to do to insert CHRM and Image Gamma.
Anyone can help me? I know my english is terrific, but I understand very well english, so if someone can write me to explain, I’ll be very happy! Thank’s
Mariateresa
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O
Odysseus
Apr 8, 2004
In article ,
(mary) wrote:

I need a little help, becouse I’ ve to make a very big work, but there is some thing I don’t understand.
I’ve 1000 photo,(3072×2040 pixel) to put on one or more CD in PNG format. Well, the customer ask me to insert chunk:
CHRM Primary chromaticities an white point
GAMA Image Gamma
TEXT Keyword, Version, Data
About text I think is good to insert by FILE-INFO file…, but I don’t know how I Have to do to insert CHRM and Image Gamma.

I don’t know any standard way to save the colour-related information except to embed a profile appropriate to the image source, whether it comes from a scanner, is in ‘generic’ sRGB or Adobe RGB, has been adjusted to a certain monitor, or whatever. I don’t think the chromaticities and gamma are particularly meaningful outside a colour-managed workflow, so if you aren’t using profiles these data should probably be omitted. Sorry, I’m not sure whether or not the PNG format even supports colour profiles.

Anyone can help me? I know my english is terrific, but I understand very well english, so if someone can write me to explain, I’ll be very happy!

"Terrific" used figuratively usually means "excellent" … perhaps "terrible" is what you were thinking of, but I don’t think your English is that bad!

—
Odysseus
H
hoffmann
Apr 9, 2004
(mary) wrote in message news:…
Hello friends,i’m writing from Italy,
I need a little help, becouse I’ ve to make a very big work, but there is some thing I don’t understand.
I’ve 1000 photo,(3072×2040 pixel) to put on one or more CD in PNG format. Well, the customer ask me to insert chunk:
CHRM Primary chromaticities an white point
GAMA Image Gamma
TEXT Keyword, Version, Data
About text I think is good to insert by FILE-INFO file…, but I don’t know how I Have to do to insert CHRM and Image Gamma.
Anyone can help me? I know my english is terrific, but I understand very well english, so if someone can write me to explain, I’ll be very happy! Thank’s
Mariateresa

Mariateresa,

I think there is some essential information missing:
Which profile is valid for each image ?
If the source images don´t have embedded profiles then one can only guess.

If some sample tests show that sRGB delivers reasonable
results then this should be told the receiver explicitly. Of course this test can hardly be done for 1000 images.

If the profile is embedded in each image then all the neces- sary information is available.
"Nobody" besides scientists needs the primary coordinates, the white point and the gamma curve explicitly.

PNG is not recommended. The widely accepted standard is TIFF.
E.g. PageMaker cannot read PNG.

Best regards –Gernot Hoffmann

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