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Ask HN: Free software for CMYK image conversion/editing?

1 points by yesenadam ↗ HN
I've got some RGB images I'd like to print, at local printer and on print on demand sites. Apparently I need to convert to CMYK for best results. Is there good free software where I can convert RGB to CMYK and then adjust the saturation, contrast, brightness etc (as CMYK)? Thank you.

(So far I only know of Scribus, but seems it can only save as CMYK, not adjust the levels.)

3 comments

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gus_massa
I use Gimp, but I think it does not support CMYK.

Searching for a while, I found that Krita supports CMYK, but I never used it.

yesenadam
Wow, thank you! Awesome, that sure sounds worth a try.

> Do NOT use screen profiles or other device profiles to draw in. Use a working space profile such as any of the ‘elle’ profiles for this, as the color maths will be much more predictable and pleasant. Krita will convert between your screen and working space on the fly, allowing you to pick the correct colors. This turns your screen into binoculars to view the image.

- seems it uses its own "working space profiles", not the usual RGB or CMYK etc, and you can export/convert from those to any other format/profile/etc even in real time. Thanks again, I'm extremely grateful. Do you accept donations?! (I searched for ages the other day and only came up with Scribus.)

https://docs.krita.org/en/general_concepts/colors/color_mana...

https://docs.krita.org/en/index.html

yesenadam
I couldn't get the first few versions I tried working (Mac High Sierra said the dmg is damaged) until I found this advice, useful for a lot more than just installing krita!:

> I’ve run into the same issue and found out there are other people getting the same error on different software. And there is a workaround on youtube. You could try to open the terminal and then type “sudo spctl --master-disable”

> This will add an additional option when you go to “Settings > Security & Privacy > Allow apps downloaded from”. You have to check “Anywhere”. Then it should work.

> Another workaround... : first test there is a quarantine flag typing in terminal "xattr /Applications/krita.app" and hit enter. the results will return “com.apple.quarantine” and maybe other results. This line is a flag and tells macos to check for signature as the file comes from the internet.

> to remove the flag type: "xattr -d com.apple.quarantine /Applications/krita.app" you can check the flag is removed by typing the first command and see the quarantine flag gone.

https://krita-artists.org/t/krita-4-4-3-start-up-error-damag...