[argyllcms] Re: Calibrating a digital photo frame

  • From: Frédéric Mantegazza <frederic.mantegazza@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 17 Dec 2007 19:55:51 +0100

On lundi 17 décembre 2007, Martin Ling wrote:

> 100 patches is not very many at all, especially for an uncalibrated LCD
> device. In my experience the targen default of 836 patches produced a
> reasonable profile for my laptop display, while increasing this to 2000
> got me better results in awkward dark areas. See also the guidance on
> patch counts in http://www.argyllcms.com/doc7/targen.html of course.

I will try to increase the number of patches...

> I think (Graham can no doubt confirm) that there's just cctiff. 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.
> I think you will probably get the best results possible by converting
> the image to TIFF, applying the colour transformation with cctiff, and
> then reconverting to JPEG using the same subsampling settings and
> quantisation tables as were used in saving the original images. The
> cjpeg tool from the libjpeg project will let you specify these settings,
> which should be possible to determine somehow from the SOF and DQT
> markers in the original image.

Ok, I'll do that. Thanks !



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