TheOtterlord

precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D tex;

void main() {

  vec4 pixColor = texture2D(tex, v_texcoord);

  // calculate the perceived brightness (https://www.101computing.net/colour-luminance-and-contrast-ratio/)
  vec4 luminance = pixColor * vec4(0.2126, 0.7152, 0.0722, 1.0);