Colour difference between GIMP and Adobe products

[balazsmarton@yahoo.co.uk]

Hi,

I have the same PDF document opened in GIMP and various Adove products (s well as in Photoshop). When I use the color picker tool the CMYK codes returned by GIMP are different from the ones returned by the other products.
For example a color returns


C 0 M 68.1 Y 76.9 K 6.7 in GIMP
C 2 M 76    Y 81   K 0    in Adobe

Why is this happening?
Note (in printing the Adobe colors look correct)

Thank you!

[sallyanne]

Probably because Gimp uses RGB colourspace whereas adobe uses CMYK

[balazsmarton@yahoo.co.uk]

(02-04-2023, 09:49 PM)sallyanne Wrote: Probably because Gimp uses RGB colourspace whereas adobe uses CMYK

Thank you! Is there any way to fix this? I think that this would be reflected in any and all color code...

[rich2005]

Really it is one way only.

Gimp is a red-green-blue (RGB) editor. You computer monitor / screen is also RGB that is what you edit in using Gimp.

Cyan-magenta-yellow (CMY) comes from the ink colours used in most printing. Colors in CMY are often muted, bright RGB  colours can not always be duplicated for printing.

You can get an impression in Gimp of what your RGB image looks like in CMY using soft proofing see: https://docs.gimp.org/2.10/en/gimp-view-...ement.html but is is an impression, the image is still RGB.

When the RGB image is converted to CMY the colours are changed, Open in Gimp and you get a CMY -> RGB equivalents not a backwards conversion. Another snag is the built-in Gimp profile sRGB.icc is different from the the others. Both Adobe and Apple have their own RGB profiles, not a lot of difference but enough for different color picker values.

This (left to right) all in Gimp,
The original RGB image
The original RGB image using soft proofing using a cmyk.icc (color profile) 
A cmyk PDF produced in Scribus, the desk-top-publishing program.

   

One problem with PDF is, as far as I know, the .icc profile is not recorded in the PDF. No way of knowing which .icc was used. You should know if you originally made the cmy image but otherwise it is a guess. Different icc profiles produce slightly different images.

If you want to edit in CMY mode use Krita, you still need to know which cmy .icc was used and one snag is while krita opens a PDF it does not export PDF.