data compression and color management
data compression and color management
- Subject: data compression and color management
- From: "joe borne" <email@hidden>
- Date: Fri, 10 Nov 2000 08:37:41 -0500
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Hi,
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Can anyone comment on how image data compression can be used in a color
managed
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workflow?
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I'm wondering specifically about two scenarios - one in which the scan
includes
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an embedded profile, and is then compressed for later use. And another in
which
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the data is transformed (either into Lab space or output space) then a profile
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is embedded, then the data is compressed.
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Any "recommended" strategies or "don't try this at home" warnings?
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I understand that the proposed JPEG 2000 will include the ability to support
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CMYK data, as well as ICC profiles that are embedded. Are there other formats
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that are already being used successfully?
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Thanks for your help,
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Greg
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>
email@hidden
Stay away from any compression method that is not totally lossless. In a
typical lossless compression system, the algorithm simply replaces redundant
data (IE: if there are five "8"'s in a row, it will replace them with
something like "8E" instead. Because E is the 5th letter.) So when your data
is uncompressed, it will return the exact same numbers. In any system that
incurs loss you will see the actual data altered in order to "cheat" it into
being smaller and sacrificing as little visual quality as possible. Since
profiling is a mathematical procedure, any alteration of data will alter the
result.
P.S. - Watch out for companies making claims of lossless compression and
better than 3 to 1 reduction in file size. If you check the fine print you
will find the term "visually lossless" (see "deceptive business practice").
--
Joe Borne
Color Consultant
(859) 282-0393