http://tour.golang.org/#36 #gohakobe

36.go

package main

import "math"
import "code.google.com/p/go-tour/pic"

func Pic(dx, dy int) [][]uint8 {
    pic := make([][]uint8, dy)
    for y := range pic {
        line := make([]uint8, dx)
        pic[y] = line
        for x := range line {
            centerX := dx/2.0
            centerY := dy/2.0
            distance := math.Sqrt(float64((centerX-x)*(centerX-x)+(centerY-y)*(centerY-y)))
            color := 0
            if (distance > float64(dx/2.0)) {
                color = 255
            } else {
                color = 0
            }
            line[x] = uint8(color)
        }
    }
    return pic
}

func main() {
    pic.Show(Pic)
}