Hi,

there seem to be some quirks in babl.

1) ./babl/base/model-cmyk.c

In the cmyk_to_rgb-function the components are assigned from the source in an erroneous order. Obviously in the CMYK-colorspace magenta is the second color. Here yellow takes its place and magenta is the third one.

double cyan = ((double *) src)[0]; double yellow = ((double *) src)[1]; double magenta = ((double *) src)[2]; double key = ((double *) src)[3];

2) ./babl/extensions/naive-CMYK.c

For what reason is there a second implementation of essentially the same code as you find it in model-cmyk.c in the file naive-CMYK.c? The only difference seems to be that model-cmyk.c makes the conversion RGB->CMYK and naive-CMYK.c implements RGBA->CMYK.
Wouldn't it be more comprehensive to have it all in one place? Or is RGB->CMYK the more basic conversion? I thought in Babl the RGBA-space were something like a reference.

3) More stunning for me: model-cmyk.c exists only in the GIT clone from git://git.gnome.org/babl but not in the downloaded tar.bz2 from ftp.gtk.org/pub/babl :-?

Sorry for my lack of understanding, Alex

On Friday 23 December 2011 12:53:18 you wrote:

Thank you for your observation. The naive-cmyk extension is the only one that should be there. As CMYK conversions go it is not good enough either which is why it is called naive (that implementation seems to have the correct component ordering as well). An extension that implements conversions through ICC profiles and perhaps lcms would be a more proper way to define a CMYK based color space and pixel format.

I'm very interested in a more ambitious implementation of the CMYK-colorspace. Also because I would like to do more experimentation with printed outputs of processed or otherwise created images. Do you have any suggestions for a good introductory work on the theory related to ICC-profiles and digital color management systems?

alex