toggle black/white filter with picom

toggle-bw.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+# pgrep returns 0 if a matching process is found, 1 if not.
+# Thus 1 means there is either a picom process without b/w filter running,
+# or none at all. Either way, display is coloured when return code is 1.
+pgrep -fa gl_FragColor &>/dev/null
+if [ $? -eq 1 ];
+then
+	pkill picom
+	picom --backend glx --glx-fshader-win \
+		"uniform sampler2D tex;
+		uniform float opacity;
+		void main() {
+		    vec4 color = texture2D(tex, gl_TexCoord[0].xy);
+		    gl_FragColor = vec4(vec3(0.2126 * color.r + 0.7152 * color.g + 0.0722 * color.b) * opacity, color.a * opacity);
+		}" &
+else
+	pkill picom
+	picom &
+fi