On Thu, Aug 12, 1999 at 04:55:30PM +0100, Nick Humphries wrote:
> From: James R Curry <[EMAIL PROTECTED]>
> >What about JPEG with the compression level set at zero?
> Yeah, that's fine.
Actually I doubt that very much, so it's better avoided. There *is* such a
thing as "lossless jpeg" but it's hardly ever used.
The cjpeg manual page has this to say.
The -quality switch lets you trade off compressed file size
against quality of the reconstructed image: the higher the
quality setting, the larger the JPEG file, and the closer
the output image will be to the original input.
[snip]
-quality 100 will generate a quantization table of all 1's,
minimizing loss in the quantization step (but there is still
information loss in subsampling, as well as roundoff error).
This setting is mainly of interest for experimental pur-
poses. Quality values above about 95 are not recommended
for normal use; the compressed file size goes up dramati-
cally for hardly any gain in output image quality.
In other words, even if you set quality to 100% the JPEG will not
be identical to the original image.
imc
