Ditter Webcam.frag

const vec3 luma = vec3(0.2126, 0.7152, 0.0722);

float round(float a){
	return floor(a + .5);
}

float dither (vec2 fragCoord) {
    float size = 3.0;
	return texture(iChannel1, fract(fragCoord / vec2(8.0*size,8.0*size))).r;
}
float quantize (float col, float steps) {
	return round(col * steps) / steps;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = fragCoord/iResolution.xy;

    // Time varying pixel color
    //vec3 col = 0.5 + 0.5*cos(iTime+uv.xyx+vec3(0,2,4));
	
    vec3 col = texture(iChannel0, uv).rgb;
    float lumi = dot(luma, col);
    
    float steps = 2.0;
    
    float c = quantize(lumi + dither(fragCoord) / steps, steps);
    
    fragColor = vec4(c,c,c, 1.0);
}