Talk:Picom
Grayscale: maybe use 30fps.net or Asahi Lina's coefficients instead of Rec. 709
According the following article using the plain Rec. 709 coefficients (0.2126, 0.7152, 0.0722) isn't ideal in sRGB color space of most x86 computers. Because Rec. 709 is meant to be applied in another way ("the standard recommends you compute a gamma-corrected grey value with gamma-corrected RGB inputs using coefficients meant for linear space").
https://30fps.net/pages/better-srgb-to-greyscale/ => 0.309, 0.609, 0.082
Asahi Lina's coefficients (also from 30fps.net) => 0.299, 0.518, 0.183
https://en.wikipedia.org/wiki/SRGB
https://github.com/bubbleguuum/toggle-monitor-grayscale/issues/8
Also some AI told me, that this Picom shader should work better in preserving other Picom compositing effects while adding grayscale. I don't fully understand it and I don't say it's better, but you might want to give it a try.
#version 330
in vec2 texcoord;
uniform sampler2D tex;
vec4 default_post_processing(vec4 c);
vec4 window_shader() {
vec2 texsize = textureSize(tex, 0);
vec4 c = default_post_processing(texture2D(tex, texcoord / texsize, 0));
float y = dot(c.rgb, vec3(0.299, 0.518, 0.183));
return vec4(y, y, y, c.a);
}