Define your own Image type, implement the necessary methods, and call pic.ShowImage. 1) Bounds should return a image.Rectangle, like image.Rect(0, 0, w, h). 2) ColorModel should return color.RGBAModel. 3) At should return a color; the value v in the last picture generator corresponds to color.RGBA{v, v, 255, 255} in this one.

go_tour_ex_image.go

package main

import (
    "code.google.com/p/go-tour/pic"
    "image"
    "image/color"
)

type Image struct{
    dx, dy int
    col func(x, y int) uint8
}

func (img *Image) ColorModel() color.Model {
    return color.RGBAModel
}

func (img *Image) Bounds() image.Rectangle {
    return image.Rect(0, 0, img.dx, img.dy)
}

func (img *Image) At(x, y int) color.Color {
    col := img.col(x, y)
    return color.RGBA{col, col, 255, 255}
}

func main() {
    m := &Image{
        dx: 255,
        dy: 255,
        col: func(x, y int) uint8 {
            return uint8(x^y)
        },
    }
    pic.ShowImage(m)
}