[argyllcms] Re: Calibrating a digital photo frame

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 18 Dec 2007 10:26:19 +1100

Martin Ling wrote:
> The fact
there's a quality option on the lcms tool at all suggests that it's
decompressing the JPEG, operating on the resulting image and then
recompressing. This is the most straightforward way of doing it but will
inevitably lead to degradation unless knowledge of the structure of the
original compressed data is used.

There's really no alternative with typical JPEGs, since 99% of them
will have had the RGB converted to YCC to allow color component
sub-sampling. The only smart thing such a program can do
is estimate the DCT quantization tables from the incoming file,
so that it can use the same quality on compression.

Graeme Gill.

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