#!/usr/bin/env bash
#
# Grayscale using picom.
# Based on https://wiki.archlinux.org/title/Picom#Grayscale

killall picom
    picom --backend glx --glx-fshader-win "
      uniform float opacity;
      uniform bool invert_color;
      uniform sampler2D tex;

      void main() {
        vec4 c = texture2D(tex, gl_TexCoord[0].xy);
        float g = (c.r + c.g + c.b) / 3.0;  // EDIT1: Average.
        c = vec4(vec3(g), c.a);  // EDIT2: Color.
        if (invert_color)
          c = vec4(vec3(c.a, c.a, c.a) - vec3(c), c.a);
        c *= opacity;
        gl_FragColor = c;
      }
    "