Subpixel‐aware downscaling filters

[dkoukola]

I’ve been playing around with subpixel‐aware downscaling filters and, for testing purposes, I’ve tried implementing them into gamescope. There are currently four filters available:

subpixel_rgb – horizontal RGB subpixel layout (3:1 ratio)
subpixel_vbgr – vertical BGR subpixel layout (3:1 ratio)
subpixel_oled – RG/B subpixel layout (2:1 ratio)
subpixel_qdoled – G/RB subpixel layout (2:1 ratio)

As of now they only work with the fixed scaling ratios listed above, i.e. they can be used like this:

gamescope -F subpixel_rgb -w 5760 -h 3240 -W 1920 -H 1080 -- <command>
gamescope -F subpixel_oled -w 3840 -h 2160 -W 1920 -H 1080 -- <command>

The aim was the highest possible quality; performance has not yet been optimized at all.

They also still produce some artifacts, such as black halos around some sharp edges, which I haven’t managed to fix yet.