[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Dmitry Kazakov]

https://bugs.kde.org/show_bug.cgi?id=356303

Dmitry Kazakov  changed:

   What|Removed |Added

  Latest Commit|https://invent.kde.org/grap |https://invent.kde.org/grap
   |hics/krita/commit/18ee2042a |hics/krita/commit/8181058a5
   |807685fa53cd0c8d95f9e4f3d41 |6ef97c0128a83ca6de10a230cfb
   |0b33|2e23

--- Comment #19 from Dmitry Kazakov  ---
Git commit 8181058a56ef97c0128a83ca6de10a230cfb2e23 by Dmitry Kazakov.
Committed on 24/08/2020 at 20:06.
Pushed by dkazakov into branch 'master'.

Add a warning message when changing profile of a multilayered image

When changing color profile of the image blending modes start to
behave differently. The biggest visual drift is caused by
the difference in tone response curves, though just changing
primaries will also affect blending modes like "Overlay".

M  +31   -0libs/image/kis_layer_utils.cpp
M  +2-0libs/image/kis_layer_utils.h
M  +1-0libs/ui/CMakeLists.txt
M  +19   -0libs/ui/dialogs/kis_dlg_image_properties.cc
M  +3-0libs/ui/dialogs/kis_dlg_image_properties.h
M  +34   -2libs/ui/forms/wdgimageproperties.ui
A  +63   -0libs/ui/widgets/KisWarningWidget.cpp [License: GPL (v2+)]
A  +46   -0libs/ui/widgets/KisWarningWidget.h [License: GPL (v2+)]
M  +2-2plugins/extensions/colorspaceconversion/colorspaceconversion.cc
M  +21   -1   
plugins/extensions/colorspaceconversion/dlg_colorspaceconversion.cc
M  +6-1   
plugins/extensions/colorspaceconversion/dlg_colorspaceconversion.h
M  +24   -2plugins/extensions/colorspaceconversion/wdgconvertcolorspace.ui

https://invent.kde.org/graphics/krita/commit/8181058a56ef97c0128a83ca6de10a230cfb2e23

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Dmitry Kazakov]

https://bugs.kde.org/show_bug.cgi?id=356303

Dmitry Kazakov  changed:

   What|Removed |Added

  Latest Commit||https://invent.kde.org/grap
   ||hics/krita/commit/18ee2042a
   ||807685fa53cd0c8d95f9e4f3d41
   ||0b33
 Status|CONFIRMED   |RESOLVED
 Resolution|--- |FIXED

--- Comment #18 from Dmitry Kazakov  ---
Git commit 18ee2042a807685fa53cd0c8d95f9e4f3d410b33 by Dmitry Kazakov.
Committed on 24/08/2020 at 20:05.
Pushed by dkazakov into branch 'krita/4.3'.

Add a warning message when changing profile of a multilayered image

When changing color profile of the image blending modes start to
behave differently. The biggest visual drift is caused by
the difference in tone response curves, though just changing
primaries will also affect blending modes like "Overlay".

M  +31   -0libs/image/kis_layer_utils.cpp
M  +2-0libs/image/kis_layer_utils.h
M  +1-0libs/ui/CMakeLists.txt
M  +19   -0libs/ui/dialogs/kis_dlg_image_properties.cc
M  +3-0libs/ui/dialogs/kis_dlg_image_properties.h
M  +34   -2libs/ui/forms/wdgimageproperties.ui
A  +63   -0libs/ui/widgets/KisWarningWidget.cpp [License: GPL (v2+)]
A  +46   -0libs/ui/widgets/KisWarningWidget.h [License: GPL (v2+)]
M  +2-2plugins/extensions/colorspaceconversion/colorspaceconversion.cc
M  +21   -1   
plugins/extensions/colorspaceconversion/dlg_colorspaceconversion.cc
M  +6-1   
plugins/extensions/colorspaceconversion/dlg_colorspaceconversion.h
M  +24   -2plugins/extensions/colorspaceconversion/wdgconvertcolorspace.ui

https://invent.kde.org/graphics/krita/commit/18ee2042a807685fa53cd0c8d95f9e4f3d410b33

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Dmitry Kazakov]

https://bugs.kde.org/show_bug.cgi?id=356303

Dmitry Kazakov  changed:

   What|Removed |Added

   Assignee|krita-bugs-n...@kde.org |dimul...@gmail.com
 CC||dimul...@gmail.com

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Storm via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

Storm  changed:

   What|Removed |Added

 CC||hewa...@gmail.com

--- Comment #17 from Storm  ---
Created attachment 95991
  --> https://bugs.kde.org/attachment.cgi?id=95991=edit
Opacity error when converting color spaces

Boud asked me to upload this here. I recently discovered that when converting
between color spaces of different gamma curve, opaque areas convert fine wile
transparent areas get screwed up: generally lightened and desaturated. It
happens either if I convert from 8 bit to 16 or 8 to 8, as long as I convert
from on-linear gamma to linear.

The layer in question has semi-transparent content, with the layer's opacity
value at 100%. I tested converting brush strokes made with a smooth edge brush,
and the inner, opaque part of the stroke converts well while the
semi-transparent edge, start and end of stroke doesn't.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Boudewijn Rempt via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #16 from Boudewijn Rempt  ---
> In my particular case that's unavoidable, as clients often require 
> multilayered
> PSD files, and 16 bit files are too large to transfer easily.  I'd work
> directly in 8 bit except the airbrush is not smooth and there's more brush 
> lag,
> but those are reports for another day. ;)

Hm, in that case, I'd say, use a gamma corrected profile even in 16
bits/channel
rgb, that way you won't get surprises when converting down to 8 bits/channel.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #11 from Chris Jones  ---
I'm changing it with Convert Image Color Space, but I get the same results with
Image Properties.  Is there somewhere else I should be changing it?

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

wolthera  changed:

   What|Removed |Added

 Resolution|WAITINGFORINFO  |---
 Ever confirmed|0   |1
 Status|NEEDSINFO   |CONFIRMED

--- Comment #12 from wolthera  ---
No, the issue shpuld be happening with both methods, because it's about final
image composition.

What this bug is about is about user expectancy, with power user vs regular
user expentancies. I need to discuss this with boud proper on how to solve
this.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #14 from wolthera  ---
Our solution will be to add a warning to the convert dialogue when doing so to
multiple layers:
https://phabricator.kde.org/T1078

The issue is that going from 16bit linear to 8bit linear will lead to far more
visible information loss than 16bit linear to 8bit srgbtrc, so the later is
preferable default behaviour.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Boudewijn Rempt via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #13 from Boudewijn Rempt  ---
Okay -- I think I get it now. I would in general warn against converting a
multilayered image from one color model to another: keep working in the color
model you are using, and only convert the final, rendered result.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #15 from Chris Jones  ---
(In reply to Boudewijn Rempt from comment #13)
> Okay -- I think I get it now. I would in general warn against converting a
> multilayered image from one color model to another: keep working in the
> color model you are using, and only convert the final, rendered result.

In my particular case that's unavoidable, as clients often require multilayered
PSD files, and 16 bit files are too large to transfer easily.  I'd work
directly in 8 bit except the airbrush is not smooth and there's more brush lag,
but those are reports for another day. ;)

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

wolthera  changed:

   What|Removed |Added

 CC||griffinval...@gmail.com

--- Comment #1 from wolthera  ---
Are you sure that the colorspace isn't linear(for example, sRGB-elle-v2-g10.icc
(the g10 means gamma=1.0, thus linear). Color maths works differently in a
linear space(It works in fact more accurately to real life physics, as real
life doesn't have the gamma crunching we impose on computer graphics)

Go to image->convert image colorspace and chose anything appended with
srgbtrc.icc(preferably srgb-elle-v2-srgbtrc.icc) to fix this.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #7 from wolthera  ---
I'm not sure, but perhaps a solution would be for the "Profile" section of the
"Convert Image Color Space" panel to switch to a srgbtrc.icc colour profile
when "Depth" is changed from 16 Bit to 8 Bit? < it should already be doing
this. Isn't it?

You should be careful with what is causing it now(and make sure to watch the
optimisations checkbox).

1. 16bit linear to/from 8bit linear should give the same results, only with
banding in the dark shades.
2. 16bit srgbtrc to/from 8bit srgbtrc should give the same results as well.
3. 16bit/8bit linear to/from 16bit/8bit srgbtrc,  should give different
results. (But it may be that the cache isn't updated yet, so toggle the layer
visibility maybe?)

Everything else is a bug.

The overlay thing is something I'll need to ask boud the specifics about, I am
curious what ps is doing there :)

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #9 from Chris Jones  ---
Well, all I know is this:

If I start with a 16 bit image using the default colour profile
(sRGB-elle-V2-g10.icc (Default)), and I change it to 8 bit, the profile
automatically changes to sRGB-elle-v2-srgbtrc.icc, which produces incorrect
results.

If I change it back to sRGB-elle-V2-g10.icc (Default) before converting though,
it produces correct results.

So unless it has adverse ramifications elsewhere, it would seem that when
starting with 16 bit using the default profile, it should stay that way when
converting to 8 bit.

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #2 from Chris Jones  ---
I'm using 16 bit with sRGB-elle-V2-g10.icc (Default), and converting to 8 bit
sRGB-elle-V2-g10.icc (Default).  If I convert to 8 bit sRGB-elle-v2-srgbtrc.icc
as you suggest, it still changes the opacity.  If I start with a 16 bit
sRGB-elle-v2-srgbtrc.icc however, it does stay the same after converting to 8
bit.

This suggests to me that the issue then is that the default settings cause
things to change unexpectedly when converting the colour depth, and if the
default settings were used to begin with, there is no apparent way within Krita
to do this without affecting the appearance of layers using Overlay.

Also, I haven't tested all of the colour profiles (there are a lot of them!),
but so far none of the ones I've tested seem to allow solid white when using
Overlay.  Do any of them?

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #3 from Chris Jones  ---
Correction: the default settings use 8 bit - the problem begins when starting
with a 16 bit image (as I typically do).

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #4 from wolthera  ---
The solid white thing is something inherit in the overlay algorithm as
referenced from the official Adobe PDF documentation. If you can't reproduce it
with photoshop, mypaint or even the css blending modes, then we have a
problem(Gimp's overlay algorithm has been non-standard for a whole version or
two, should be fixed in 2.8).

I need you to do something really really dumb. Could you go to
settings->configure Krita->color management. And then just -look- at the page
and press ok.

Then try to reproduce your bug?

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[Chris Jones via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #6 from Chris Jones  ---
Wait a sec - that's what it does already!  Sorry, getting confused. :)

When I select 8 Bits in the "convert Image Color Space" panel, it also
automatically changes the Profile to sRGB-elle-v2-srgbtrc.icc - and maybe
that's the problem right there.  Shouldn't it retain the same profile that the
image already uses?

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[krita] [Bug 356303] Overlay blend mode appears incorrect in a 16 bit image

[wolthera via KDE Bugzilla]

https://bugs.kde.org/show_bug.cgi?id=356303

--- Comment #8 from wolthera  ---
Ah! Sorry.

Well, maybe? Or maybe not? We are having a ball deciding the best behaviour
that avoids people coming to us to tell us their images look strange.

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