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: Andrew Rodney <email@hidden>
- Date: Wed, 02 Aug 2006 06:49:18 -0600
- Thread-topic: `Lossless' retroactive embedding of color profile (avoid JPEG recompression); basic color profile theory
On 8/2/06 1:18 AM, "john castronovo" wrote:
> 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?
Better. Worse? Its different. The pixels have been recompressed and that's
the issue. That's what happens with JPEG. At least though Photoshop (and
apparently when using UNIX or OSX to embed the profile in the document).
This doesn't happen with TIFF or PSD or similar file formats that don't
recompute how to handle the pixel values.
> On 8/2/06 1:33 AM, "Graeme Gill" wrote:
>> It's easy enough to do the experiment (and I've done it). Get an original,
>> save it as JPEG in Photoshop with a given compression. Close it. Open it.
>> Save it as TIFF. Close it. Open it. Save it as JPEG etc. Use the
>> Image/Calculation
>> to diff the plane values from successive TIFF's. Track the number of pixels
>> in the diff that are not 0. Each time, fewer and fewer pixels change.
But they do change. So what about doing this over and over again but instead
of JPEG, use PSD and TIFF?
Andrew Rodney
http://www.digitaldog.net/
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