uniform float intensity = 0.004;

highp float rand(vec2 co) {
    highp float a = 12.9898;
    highp float b = 78.233;
    highp float c = 43758.5453;
    highp float dt= dot(co.xy ,vec2(a,b));
    highp float sn= mod(dt,3.14);
    return fract(sin(sn) * c);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
    vec2 uv = fragCoord.xy / iResolution.xy;
    vec4 fetch = texture(iChannel0, uv + intensity * rand(uv));
    fragColor = fetch;
}