package color

const (
	ChromaSamplePositionUnspecified ChromaSamplePosition = iota
	ChromaSamplePositionLeft
	ChromaSamplePositionCenter
	ChromaSamplePositionTopLeft
	ChromaSamplePositionTop
	ChromaSamplePositionBottomLeft
	ChromaSamplePositionBottom
	ChromaSamplePositionNB
)

type ChromaSamplePosition byte

// ChromaSampling The subsampling scheme is commonly expressed as a three-part ratio J : A : B (e.g. 4:2:2), that describe the number of luminance and chrominance samples in a conceptual region that is J pixels wide and 2 pixels high.
type ChromaSampling struct {
	// J horizontal sampling reference (width of the conceptual region). Usually, 4.
	J byte
	// A number of chrominance samples (Cb, Cr) in the first row of J pixels.
	A byte
	// B number of changes of chrominance samples (Cb, Cr) between first and second row of J pixels. Note that B has to be either zero or equal to A
	B byte
}

// ElementPixels returns the number of pixels for a full element
func (s ChromaSampling) ElementPixels() int {
	return int(s.J) * 2
}

// ElementSamples returns the number of actual samples (total Y, Cb, Cr) for an encoded element
func (s ChromaSampling) ElementSamples() int {
	return int(s.J)*2 + s.ElementChromaSamples()
}

func (s ChromaSampling) ElementChromaSamples() int {
	return int(s.A)*2 + int(s.B)*2
}

func (s ChromaSampling) PlaneLumaSamples(width, height int) int {
	return width * height
}

func (s ChromaSampling) PlaneCrSamples(width, height int) int {
	return int((int64(width) * int64(height) * (int64(s.A) + int64(s.B))) / int64(s.ElementPixels()))
}

func (s ChromaSampling) PlaneCbSamples(width, height int) int {
	return int((int64(width) * int64(height) * (int64(s.A) + int64(s.B))) / int64(s.ElementPixels()))
}