Bug 153813 - radial gradient with transition start renders wrongly in automatic steps if Skia is enabled
Summary: radial gradient with transition start renders wrongly in automatic steps if S...
Status: NEW
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: Writer (show other bugs)
(earliest affected) alpha0+
Hardware: All All
: medium normal
Assignee: Not Assigned
Depends on:
Blocks: Object-Fill-Gradient Skia
  Show dependency treegraph
Reported: 2023-02-24 21:28 UTC by Regina Henschel
Modified: 2023-02-26 20:57 UTC (History)
4 users (show)

See Also:
Crash report or crash signature:

automatic steps vs maximal steps (19.27 KB, application/vnd.oasis.opendocument.text)
2023-02-24 21:28 UTC, Regina Henschel
Screenshot Skia enabled (19.00 KB, application/vnd.oasis.opendocument.text)
2023-02-24 21:31 UTC, Regina Henschel

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Description Regina Henschel 2023-02-24 21:28:29 UTC
Created attachment 185577 [details]
automatic steps vs maximal steps

Open attached file. The shapes have a radial gradient with transition start (border) 50%. If Skia is enabled the border is not only outer but also inside the gradient. If Skia is disabled the shape looks the same as with maximal steps, which is the expected rendering.

Disable anti-aliasing, otherwise you get moire effects in case of rendering with maximal steps.
Comment 1 Regina Henschel 2023-02-24 21:31:51 UTC
Created attachment 185578 [details]
Screenshot Skia enabled
Comment 2 m_a_riosv 2023-02-24 22:19:54 UTC
Version: (X86_64) / LibreOffice Community
Build ID: ab20dba30769a5a52830220daa347772485db6a2
CPU threads: 4; OS: Windows 10.0 Build 19045; UI render: default; VCL: win
Locale: es-ES (es_ES); UI: en-US Calc: CL threaded Jumbo
Comment 3 m_a_riosv 2023-02-24 22:23:10 UTC
Anyway, what looks to me very problematic it's the affecting by the Antialiasing.
Comment 4 V Stuart Foote 2023-02-24 23:01:17 UTC
Also confirming, With Skia Vulka or Skia raster libs rendering, using an increment value for the area gradient it is not as smooth as the "auto" checkbox achieves.

Checked at each of 16, 32, 64, 128 and 256 level gradient.

CPU GDI rendering, or with CPU HA those gradient steps increase in smoothness through 256 increments, matching the "automatic" at about 128 steps.

The Skia based rendering of the gradient steps also increase--but they do not smooth out. So at 256 steps, still noticeable moiré and coarseness to the gradient. 

Did similar for  https://git.libreoffice.org/core/+/a46cb5dc607d1d1af402ff3e8fce731e7427854d%5E%21 for bug 137523 for the liner gradients need to be done for radial area gradients?
Comment 5 V Stuart Foote 2023-02-24 23:13:24 UTC
Seems related, or even a dupe to bug 151328 and its bisect to

Comment 6 V Stuart Foote 2023-02-24 23:17:45 UTC
(In reply to V Stuart Foote from comment #4

s/ bug 137523/ bug 136523