protected override byte GetValue(int index)
{
//return (Math.Round((double)(this[index + RedIndex] + this[index + GreenIndex] + this[index]) / 3) < 128)
return((ColorExtensions.GetBt601Value(this[index + RedIndex], this[index + GreenIndex], this[index]) < 128)
? Byte.MinValue : Byte.MaxValue);
}