package thumbnail

import (
	"image/color"
)

func Blend(a, b color.Color) color.Color {
	switch a.(type) {
	case color.RGBA:
		return BlendRGBA(a.(color.RGBA), b.(color.RGBA)) // FIXME there's syntax for this

	case color.YCbCr:
		return BlendYCbCr(a.(color.YCbCr), b.(color.YCbCr))

	default:
		return a // ??? unknown color format
	}
}

func BlendYCbCr(a, b color.YCbCr) color.YCbCr {
	return color.YCbCr{
		Y:  uint8((int(a.Y) + int(b.Y)) / 2),
		Cb: uint8((int(a.Cb) + int(b.Cb)) / 2),
		Cr: uint8((int(a.Cr) + int(b.Cr)) / 2),
	}
}

func BlendRGBA(a, b color.RGBA) color.RGBA {
	return color.RGBA{
		R: uint8((int(a.R) + int(b.R)) / 2),
		G: uint8((int(a.G) + int(b.G)) / 2),
		B: uint8((int(a.B) + int(b.B)) / 2),
		A: uint8((int(a.A) + int(b.A)) / 2),
	}
}