bloom.frag

precision mediump float;

// texcoords from the vertex shader
varying vec2 vTexCoord;

// our textures coming from p5
uniform sampler2D tex0;
uniform sampler2D tex1;

// value between 0 and 1
uniform float bloomAmount;

void main() {

    vec2 uv = vTexCoord;
    // the texture is loaded upside down and backwards by default so lets flip it
    uv = 1.0 - uv;

    // get the camera and the blurred image as textures
    vec4 cam = texture2D(tex0, uv);
    vec4 blur = texture2D(tex1, uv);

    // calculate an average color for the blurred image
    // this is essentially the same as saying (blur.r + blur.g + blur.b) / 3.0;
    float avg = dot(blur.rgb, vec3(0.33333));

    // mix the blur and camera together according to how bright the blurred image is
    // use the mouse to control the bloom
    vec4 bloom = mix(cam, blur, clamp(avg*(1.0 + bloomAmount), 0.0, 1.0));

    gl_FragColor = bloom;
}