[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Henrik Fehlauer]

https://bugs.kde.org/show_bug.cgi?id=354542

--- Comment #10 from Henrik Fehlauer  ---
> 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?

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Huon]

https://bugs.kde.org/show_bug.cgi?id=354542

--- Comment #9 from Huon  ---
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.

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Huon]

https://bugs.kde.org/show_bug.cgi?id=354542

Huon  changed:

   What|Removed |Added

 Ever confirmed|0   |1
 Status|UNCONFIRMED |CONFIRMED

--- Comment #8 from Huon  ---
(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.

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Raghavendra kamath]

https://bugs.kde.org/show_bug.cgi?id=354542

--- Comment #7 from Raghavendra kamath  ---
Created attachment 112020
  --> https://bugs.kde.org/attachment.cgi?id=112020=edit
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

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Raghavendra kamath]

https://bugs.kde.org/show_bug.cgi?id=354542

--- Comment #6 from Raghavendra kamath  ---
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.

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Huon]

https://bugs.kde.org/show_bug.cgi?id=354542

--- Comment #5 from Huon  ---
(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.

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Henrik Fehlauer]

https://bugs.kde.org/show_bug.cgi?id=354542

Henrik Fehlauer  changed:

   What|Removed |Added

 CC||rk...@lab12.net

--- Comment #4 from Henrik Fehlauer  ---
> 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? ;)

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Huon]

https://bugs.kde.org/show_bug.cgi?id=354542

Huon  changed:

   What|Removed |Added

 CC||h...@plonq.org

--- Comment #3 from Huon  ---
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?

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[gwenview] [Bug 354542] [Wishbug] Ability to show proper CMYK colors embedded in files like Krita

[Nate Graham]

https://bugs.kde.org/show_bug.cgi?id=354542

Nate Graham  changed:

   What|Removed |Added

 CC||pointedst...@zoho.com

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