rhythmbullet/android/assets/shaders/gaussian_blur.fsh

#version 330 core
#ifdef GL_ES
#define LOWP lowp
precision mediump float;
#else
#define LOWP
#endif

varying LOWP vec4 vColor;
varying vec2 vTexCoord;

uniform int horizontal;
uniform sampler2D u_texture;
uniform float weight[5] = float[] (0.227027, 0.1945946, 0.1216216, 0.054054, 0.016216);

void main() {
  vec2 tex_offset = 1.0 / textureSize(u_texture, 0);
  vec4 color = texture(u_texture, vTexCoord);
  vec3 result = color.rgb * weight[0];

  if (horizontal == 1) {
    for (int i = 1; i < 5; ++i) {
      result += texture(u_texture, vTexCoord + vec2(tex_offset.x * i, 0.0)).rgb * weight[i];
      result += texture(u_texture, vTexCoord - vec2(tex_offset.x * i, 0.0)).rgb * weight[i];
    }
  } else {
    for (int i = 1; i < 5; ++i) {
      result += texture(u_texture, vTexCoord + vec2(0.0, tex_offset.y * i)).rgb * weight[i];
      result += texture(u_texture, vTexCoord - vec2(0.0, tex_offset.y * i)).rgb * weight[i];
    }
  }

  gl_FragColor = vec4(result, color.a);
}