code: func convertImage(dest *Image, src image.Image) {
  	var r, g, b, a uint32
  	var x, y, i int
  
  	for x = dest.Rect.Min.X; x < dest.Rect.Max.X; x++ {
  		for y = dest.Rect.Min.Y; y < dest.Rect.Max.Y; y++ {
  			r, g, b, a = src.At(x, y).RGBA()
  			i = dest.PixOffset(x, y)
  			dest.Pix[i+0] = uint8(b >> 8)
  			dest.Pix[i+1] = uint8(g >> 8)
  			dest.Pix[i+2] = uint8(r >> 8)
  			dest.Pix[i+3] = uint8(a >> 8)
  		}
  	}
  }
docs: // convertImage converts any image implementing the image.Image interface to
  // an xgraphics.Image type. This is *slow*.