kernel vec4 blackAndWhite (sampler src, float redPercentage, float greenPercentage, float bluePercentage)  __attribute__ ((preserves_opacity))
{
	vec4 p = unpremultiply(sample(src, samplerCoord(src)));
	p.rgb = vec3(p.r * redPercentage + p.g * greenPercentage + p.b * bluePercentage);
	return premultiply(p);
}
