Re: Photoshop 7 JPEG bug
Re: Photoshop 7 JPEG bug
- Subject: Re: Photoshop 7 JPEG bug
- From: Graeme Gill <email@hidden>
- Date: Wed, 10 Jul 2002 15:17:58 +1000
Dave Camp wrote:
>
Hmm. They want to use maximum compression, but don't want any artifacts.
>
That doesn't seem very realistic. That would be the holy grail of image
>
compression...
But are we talking artefacts, or straight out implementation
errors here ?
The DC component of a JPEG image is usually quantized to 12 bit
precision, and although you may loose edge detail at high
compression ratios, large areas of white should maintain
a precision of better than 1 part in 100.
I did a quick check using Photoshop 5.5 on a CMYK file.
Even on quality 0 (which gives horrible DCT block artefacts),
the large area white background was still exactly white.
Graeme Gill.
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