https://bugs.kde.org/show_bug.cgi?id=466026
Bug ID: 466026
Summary: Spectacle screenshot scales cross-monitor content with
artifacts
Classification: Plasma
Product: kwin
Version: 5.27.0
Platform: Archlinux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: ye.jingc...@gmail.com
Target Milestone: ---
Created attachment 156454
--> https://bugs.kde.org/attachment.cgi?id=156454&action=edit
cross monitor screenshot, left@2x, right@1.5x
SUMMARY
(This is continued from https://bugs.kde.org/show_bug.cgi?id=460675, but might
not be related)
I have two monitors side by side, the left one scaled at 200%, the right one
150%. If Spectacle capture a rectangle region screenshot containing parts from
both monitors, the part containing 150% monitor is scaled with artifacts not
present on screen.
If the rectangle is entirely within either monitor, the result is the same as
on screen.
STEPS TO REPRODUCE
1. Create the above monitor setup.
2. Open a integer scaled window (Dolphin or Gwenview, which doesn't support the
new fractional-scale protocol yet), put it across monitor border.
3. Use spectacle to capture a rectangle region containing the window above,
across monitor border.
4. Save and see the resulting screenshot without scaling **on a integer scaled
monitor**
OBSERVED RESULT
The right half (from 150% scaled monitor) contains weird artifacts, especially
on texts. (See attachment "left@2x, ri...@1.5x.png")
EXPECTED RESULT
The right half should match as closely as possible to what is seen to the eye,
without those artifacts.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 5.27.0
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
ADDITIONAL INFORMATION
I just realized when experimenting with Spectacle, that in order for the window
to maintain its shape across monitors in screenshot, some scaling must be done
after capturing both monitors. So the resulting artifacts on the right half is
(probably) caused by Spectacle scaling up the 150% half, which is already
scaled down from 200% by kwin, to match the 200% half. The only problem is the
scaling algorithm that introduced those artifacts.
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