[argyllcms] profile: black generation

  • From: Klaus Karcher <lists@xxxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 31 Dec 2005 02:35:31 +0100

Hello Graeme,

thanks for the quick reply concerning xicclu. It behaves now as expected (at least for my comprehension ;-).

Now I have a question regarding black generation (Singular Value Decomposition):

Converting one of my favorite gamut mapping test images (the hull of a RGB Cube) to CMYK, I noticed that although the composite view of the result looks smoothly and coherently, viewing each canal separately shows a undulating surface.

I've made a web page to illustrate this: see

The only way to avoid the problem seems to set black generation to zero or max -- increasing the quality parameter only reduces the wavelength of the oscillation and using profile's new "-r" parameter or varying the "smth" variable in gammap.c seems to have almost no influence on the issue.

Therefore I think the root of the problem must be somewhere in the svd code. Do you have any hints on how it can be amended?

thanks in advance,

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