| Summary: | Show proper CMYK colors embedded in files like Krita | ||
|---|---|---|---|
| Product: | [Applications] gwenview | Reporter: | Raghavendra kamath <raghu> |
| Component: | general | Assignee: | Gwenview Bugs <gwenview-bugs-null> |
| Status: | CONFIRMED --- | ||
| Severity: | normal | CC: | Fahad.alsaidi, huon, myriam, nate, null, wzc782970009 |
| Priority: | NOR | ||
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Platform: | Other | ||
| OS: | Linux | ||
| Latest Commit: | Version Fixed In: | ||
| Sentry Crash Report: | |||
| Attachments: |
sample CMYK tiff
Sample CMYK jpg Screenshot showing different colors |
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Description
Raghavendra kamath
2015-10-29 08:57:24 UTC
Created attachment 95202 [details]
sample CMYK tiff
Created attachment 95203 [details]
Sample CMYK jpg
I can't reproduce, CMYK seems to be rendering correctly in Gwenview. I found https://phabricator.kde.org/R260:bfc55ac46375070b705402ecc16dfb989134e78c which seemed to fix this in 2008. Raghavendra if you're still around, are you still having this problem? > I can't reproduce, CMYK seems to be rendering correctly in Gwenview. Try opening the images in Gwenview, Krita, Firefox and Chromium. For me they look different, possibly because of varying levels of support for the embedded colour profile "exiftool" tells me about. > which seemed to fix this in 2008 But the bug was reported for 15.08.2, which is from 2015, so it should include the fix already, shouldn't it? ;) (In reply to Henrik Fehlauer from comment #4) > > I can't reproduce, CMYK seems to be rendering correctly in Gwenview. > Try opening the images in Gwenview, Krita, Firefox and Chromium. For me they > look different, possibly because of varying levels of support for the > embedded colour profile "exiftool" tells me about. I didn't test with enough applications obviously :(. So I tried the jpg in Chromium, Firefox, qutebrowser, Gwenview, KolorPaint, Krita. All looked 'cyan' except for Chromium and Krita, which looked 'blue'. So all the 'cyan' ones are wrong? Quite surprising if so. Hi Huon
I am now using Version 17.12.3 and the bug is still reproducible.
> All looked 'cyan' except for Chromium and Krita, which looked 'blue'. So all the 'cyan' ones are wrong? Quite surprising if so.
Yes the aqua blue image you are seeing is wrong one. Krita and chromium are showing correct colors.
I'll attach a recent screen shot since my original screenshots are deleted.
Created attachment 112020 [details]
Screenshot showing different colors
The screenshot shows the jpg in gwenview on left and in krita on right. I have highlighted the color profile information in Krita
(In reply to Raghavendra kamath from comment #7) > Created attachment 112020 [details] > Screenshot showing different colors > > The screenshot shows the jpg in gwenview on left and in krita on right. I > have highlighted the color profile information in Krita Thanks for the extra info. I'll tackle this soon. So I looked into this. Seems like it's beyond me right now. Qt (QImage) obviously doesn't support proper CMYK support, so we'd have to do things manually. And my lack of knowledge in this area means I wouldn't know where to start with that. Plus I'm not sure if I really understand the problem - Gwenview displays pure cyan correctly. But I'm guessing what Krita and Chromium do is display the closest possible color to what you'd see when printing? Anyway, afraid to say I'm not able to fix this right now. > I'm not able to fix this right now. It's okay, thanks for trying ;) Maybe someone else will eventually pick up the bug. https://en.wikipedia.org/wiki/Channel_(digital_image)#CMYK_color_sample is a bit sparse, but perhaps there are other resources with more information. > I'm guessing what Krita and Chromium do Don't forget that you can look at the source. Also Krita folks are quite approachable, you could try asking them how they did things. > we'd have to do things manually Maybe something can be done via KImageFormats? The CMYK->RGB conversion formulars are likely wrong, probably copied from old Qt versions. (In reply to Christoph Feck from comment #11) > The CMYK->RGB conversion formulars are likely wrong, probably copied from > old Qt versions. Gwenview doesn't use any explicit formulas. So unless QColor::fromCmyk(), and the countless CMYK - RGB conversion formulas and charts available on the internet are wrong, then this isn't the case. As far as I found out, this is due to lack of color management. If you want to get more insight about Krita's color management, you can ping boud or wolthera on #krita (freenode), I am sure that they'll help. Apart from CMYK support , there seems to be lack of color management too. Incidentally "Showfoto" from digikam has color management (RGB Only) May be we can check how it works? Okular has the same problem. |