Heavy aliasing when downscaling on qt6 with fractional scaling enbaled.

[Rabcor]

Edit: This seems to be a qt6 issue, setting QT_SCALE_FACTOR_ROUNDING_POLICY=RoundPreferFloor seems to fix the problem.

Left: Downscaled image in qimgv, Right: Same image downscaled in mpv

I had a similar issue with lximage-qt (but it wasn't just for scaling, it was present at 1:1 scale too although i think it was only for gifs)

The issue is only present when using qt6. I am using the latest git build.

qimgv -v
QGuiApplication::setDesktopFileName: the specified desktop file name ends with .desktop. For compatibility reasons, the .desktop suffix will be removed. Please specify a desktop file name without .desktop suffix
qimgv 1.0.3

I have figured out what's causing it, it's fractional scaling in wayland.

E.g. in my hyprland settings if ii configure my display to be at 1:1 scale monitor=eDP-2,[email protected],0x0,1, vrr, 1

The problem goes away.

(I mean there is still some difference but that could be explained with sclaing algorithms, mpv is using lanczos which is superior to everything offered by qimgv)