precision mediump float;

#endif

​

uniform vec2 u_resolution;

uniform float u_time;

uniform vec2 u_mouse;

uniform sampler2D u_img;

​

float amount = 0.7;

​

float random2D(vec2 coord) {

  return fract(sin(dot(coord.xy, vec2(12.9898, 78.233))) * 43758.5453);

}

​

void main() {

  vec2 coord = gl_FragCoord.xy / u_resolution;

  vec3 color = vec3(0.0);

  vec4 image = texture2D(u_img, coord);

  float noise = (random2D(coord) - 0.5) * amount;

  image.r += noise;

  image.g += noise;

  image.b += noise;

  gl_FragColor = image;

}