Extended Version of a Example in Kernighan Book

Madelbrot.go

package main

import (
	"flag"
	"image"
	"image/color"
	"image/png"
	"math/cmplx"
	"os"
	// "math"
	"runtime"
	"sync"
	"time"
)

const (
	xmin, ymin, xmax, ymax = -2, -2, 2, 2
)

func main() {
	// Let Go to use all CPU cores
	runtime.GOMAXPROCS(runtime.NumCPU())

	var mu sync.Mutex

	// Parse command arguments
	var width = flag.Int("w", 400, "Width of output image")
	var height = flag.Int("h", 400, "Height of output image")
	flag.Parse()

	stepX := (xmax - xmin) / float64(*width)
	stepY := (ymax - ymin) / float64(*height)

	// Create Image Variable
	img := image.NewRGBA(image.Rect(0, 0, *width, *height))

	for y := 0; y < *height; y++ {
		go plotX(y, stepX, stepY, width, img, mu)
	}

	// Write to file
	fileName := time.Now().Format(time.RFC3339) + ".png"

	fp, err := os.Create(fileName)
	defer fp.Close()

	if err != nil {
		panic(err)
	}

	png.Encode(fp, img)
}

func plotX(y int, stepX float64, stepY float64, width *int, img *image.RGBA, mu sync.Mutex) {
	yInCPlane := stepY*float64(y) + ymin
	for x := 0; x < *width; x++ {
		xInCPlane := stepX*float64(x) + xmin
		z := complex(xInCPlane, yInCPlane)

		mu.Lock()
		img.Set(x, y, mandelbrot(z))
		mu.Unlock()
	}
}

func mandelbrot(z complex128) color.Color {
	var v complex128

	for i := uint8(0); i <= 127; i++ {
		v = v*v + z
		if cmplx.Abs(v) > 2 {
			return colorCreator(i)
		}
	}

	return color.Black
}

func colorCreator(step uint8) color.RGBA {
	return color.RGBA{255 - step*10, 127 - step*10, step * 10, 0xFF}
}

I must work on coloring and zooming features.