kernel vec4 normalizeImage (sampler src, float minValue, float maxValue)  __attribute__ ((preserves_opacity))
{
	vec4 p =  unpremultiply(sample(src, samplerCoord(src)));

	vec3 minVec = vec3(minValue);
	vec3 maxVec = vec3(maxValue);
	vec3 denom = (maxVec - minVec);

	p.rgb = (p.rgb - minVec.rgb) / denom;
	return premultiply(p);
}
