Function adjustOpacity

plugin/klala/draw.go:341–354

adjustOpacity 更改透明度

(m image.Image, percentage float64)

// adjustOpacity 更改透明度
func adjustOpacity(m image.Image, percentage float64) image.Image {
	bounds := m.Bounds()
	dx, dy := bounds.Dx(), bounds.Dy()
	nimg := image.NewRGBA64(bounds)
	for i := 0; i < dx; i++ {
		for j := 0; j < dy; j++ {
			r, g, b, a := m.At(i, j).RGBA()
			opacity := uint16(float64(a) * percentage)
			r, g, b, a = nimg.ColorModel().Convert(color.NRGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: opacity}).RGBA()
			nimg.SetRGBA64(i, j, color.RGBA64{R: uint16(r), G: uint16(g), B: uint16(b), A: uint16(a)})
		}
	}
	return nimg
}