Bug in NewImageFromImage function?

[imprity]

If you look at NewImageFromImage, it converts color weirdly.

func NewImageFromImage(img image.Image) *Image {
	size := img.Bounds().Size()

	cx := (C.int)(size.X)
	cy := (C.int)(size.Y)
	ccolor := colorCptr(White)
	ret := C.GenImageColor(cx, cy, *ccolor)

	for y := 0; y < size.Y; y++ {
		for x := 0; x < size.X; x++ {
			color := img.At(x, y)
			r, g, b, a := color.RGBA()
			rcolor := NewColor(uint8(r), uint8(g), uint8(b), uint8(a))
			ccolor = colorCptr(rcolor)

			cx = (C.int)(x)
			cy = (C.int)(y)
			C.ImageDrawPixel(&ret, cx, cy, *ccolor)
		}
	}
	v := newImageFromPointer(unsafe.Pointer(&ret))
	return v
}

when it really should be

func NewImageFromImage(img image.Image) *Image {
	size := img.Bounds().Size()

	cx := (C.int)(size.X)
	cy := (C.int)(size.Y)
	ccolor := colorCptr(White)
	ret := C.GenImageColor(cx, cy, *ccolor)

	for y := 0; y < size.Y; y++ {
		for x := 0; x < size.X; x++ {
			color := img.At(x, y)
			r, g, b, a := color.RGBA()

			// DIFF HERE ================================
			rcolor := NewColor(uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8))
			// ==========================================

			ccolor = colorCptr(rcolor)

			cx = (C.int)(x)
			cy = (C.int)(y)
			C.ImageDrawPixel(&ret, cx, cy, *ccolor)
		}
	}
	v := newImageFromPointer(unsafe.Pointer(&ret))
	return v
}

That's how image/color package does it.

func rgbaModel(c Color) Color {
	if _, ok := c.(RGBA); ok {
		return c
	}
	r, g, b, a := c.RGBA()
	return RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
}

Reason I'm posting here instead of making an issue post is because I'm not sure if it's a bug or a clever optimization.

Since the code works well if underlying image color is RGBA or NRGBA, which will be the case for most images.

[JupiterRider]

@imprity This definitely is a bug! Thanks for finding it.

I cloud reproduce this with some .png Images and always reproduce for .jpeg (color.YCbCr).

Feel free to open a pull request.

[imprity]

Yup, made a pull request. #414