来自golang tour 练习 https://tour.go-zh.org/methods/16

package mainimport "golang.org/x/tour/pic"import "image"import "image/color"type Image struct{}func (im Image) ColorModel() color.Model {    return color.RGBAModel}func (im Image) Bounds() image.Rectangle {    return image.Rect(0, 0, 200, 200)}func (im Image) At(x, y int) color.Color {    return color.RGBA{uint8((x^y)/2), uint8((x+y)/2), 255, 255}}func main() {	m := Image{}	pic.ShowImage(m)}