[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2020-08-20 Thread Dmitry Kazakov
https://bugs.kde.org/show_bug.cgi?id=414386

Dmitry Kazakov  changed:

   What|Removed |Added

 Status|CONFIRMED   |RESOLVED
 Resolution|--- |NOT A BUG
   Assignee|krita-bugs-n...@kde.org |dimul...@gmail.com
   See Also||https://bugs.kde.org/show_b
   ||ug.cgi?id=410516

--- Comment #8 from Dmitry Kazakov  ---
Okay, the bug looks really interesting, but I don't think we can fix it without
changing behavior and speed of existing blending modes.

The only exception is 'Luminosity / Shine (SAI)', but it has its own bugreport
in bug 410516.

And since the big does not cause any real workflow problems to the reporter, I
guess we can just close it :)

Thank you, acc4commissions, for a really interesting observation! :)

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2020-04-24 Thread bugzilla_noreply
https://bugs.kde.org/show_bug.cgi?id=414386

--- Comment #7 from acc4commissi...@gmail.com ---
(In reply to wolthera from comment #6)
> I guess confirmed.

As a user I don't even consider this an issue to be honest. I doesn't cause any
problem in the actual painting process. Like I said I reported this because it
seemed related to another bug(410516), but yeah, I'm not against fixing it
either...

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2020-04-24 Thread wolthera
https://bugs.kde.org/show_bug.cgi?id=414386

wolthera  changed:

   What|Removed |Added

 Ever confirmed|0   |1
 CC||griffinval...@gmail.com
 Status|REPORTED|CONFIRMED

--- Comment #6 from wolthera  ---
I guess confirmed.

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2019-11-27 Thread bugzilla_noreply
https://bugs.kde.org/show_bug.cgi?id=414386

--- Comment #5 from acc4commissi...@gmail.com ---
> > Plus, there's this weird black triangles appears in vector text areas...
> 
> Yes, it is a bug and should be fixed. It would be better if you added a
> separate ticket for that.

https://bugs.kde.org/show_bug.cgi?id=414581

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2019-11-21 Thread bugzilla_noreply
https://bugs.kde.org/show_bug.cgi?id=414386

--- Comment #4 from acc4commissi...@gmail.com ---
Actually I don't care about this particular bug. I just reported it because it
seemed related to 410516. :)

So if you need to ignore this for any development purpose I won't mind. Just
hope this report helped.

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2019-11-21 Thread Dmitry Kazakov
https://bugs.kde.org/show_bug.cgi?id=414386

Dmitry Kazakov  changed:

   What|Removed |Added

 CC||dimul...@gmail.com

--- Comment #3 from Dmitry Kazakov  ---
Hi, acc4commisions!

That is a very interesting report :) I've never though about these effects.
Most of them are the consequence of the design decisions we did for
optimization purposes. So before explaining them I would like to ask you, what
is your workflow? Why do you want these edges to be smooth?


Detailed explanation:

> 'Normal' produces blocky edges.

By definition, when alpha is null, the value of color channels is undefined (in
normal user workflow). Therefore, if we know that the destination alpha is
null,  we just copy the color of source channels, disregarding alpha. It is
faster, and normal users will not see the difference.

And you see blocky edges, because in "Normal" composite op we don't operate on
individual pixels, but on strides of 8(!) pixels (due to AVX CPU
optimizations). If you go to Settings->Performance->Disable AVX Optimizations
and restart Krita you'll see that the edges become less blocky, like in
"Overlay", but without artifacts.

> 'Overlay', ... etc produces sharp edges with artifacts

It happens because of a division in 8-bit numerical space. When alpha is low,
then division/multiplication operations become non-stable. If you switch to
32-bit float color space, then the bug will disappear. Theoretically, we can
try to fix it: Normal doesn't have this effect, though it has a little bit
different blending. Though it might take quite a bit of time with uncertain
results.

> Only 'Luminosity / Shine (SAI)' produces the smooth result

It is actually a bug in 'Luminosity / Shine (SAI)' and it should be fixed with
410516 :) This blending mode blends-in black color into the edges, which makes
the edge look smooth. Just compare the strokes on white background.

> Plus, there's this weird black triangles appears in vector text areas...

Yes, it is a bug and should be fixed. It would be better if you added a
separate ticket for that.

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2019-11-21 Thread bugzilla_noreply
https://bugs.kde.org/show_bug.cgi?id=414386

--- Comment #2 from acc4commissi...@gmail.com ---
Created attachment 124059
  --> https://bugs.kde.org/attachment.cgi?id=124059=edit
(capture) resulting edges

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[krita] [Bug 414386] 'Split Alpha' creates unexpected edges with some brush blending modes

2019-11-21 Thread bugzilla_noreply
https://bugs.kde.org/show_bug.cgi?id=414386

--- Comment #1 from acc4commissi...@gmail.com ---
Created attachment 124058
  --> https://bugs.kde.org/attachment.cgi?id=124058=edit
(capture) black artifacts in vector text areas

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