Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
- Subject: Re: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
- From: "john castronovo" <email@hidden>
- Date: Wed, 2 Aug 2006 03:18:24 -0400
----- Original Message -----
From: "Marco Ugolini"
In a message dated 8/1/06 11:54 PM, john castronovo wrote:
From: "Graeme Gill"
Certainly if you continue to open and close (decompress
and compress) the same JPEG file with the same quantisation
table (usually the same program quality setting), then there
is no additional loss for each round.
Suppose the new file is saved with a better quality setting than the
first. I wouldn't expect it to get better of course, but could the
change in settings actually do some damage?
Even the highest quality setting in JPEG causes a detectable amount of
damage to a file, which is compounded with each successive action of
saving.
While this amount of damage at the highest setting is not serious for
most
purposes (and less than it used to be a few years ago), it may become
noticeable after being compounded by a number of saves.
It's best to save in PSD or TIFF format, not to make things worse.
Sure, but Graeme implied that no additional damage would be done if the
jpeg quality setting was kept the same for each save. Certainly it would
be worse if the quality setting was lowered, but would it also be bad if
it were changed to a higher setting than it originally was?
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