// Written by xojoc <http://xojoc.pw>. Public domain.
package main

import (
	"image"
	"image/color"
	"image/png"
	"math/cmplx"
	"os"
)

const (
	w    = 700
	h    = 500
	maxi = 50
)

func main() {
	img := image.NewRGBA(image.Rect(0, 0, w, h))

	// Where the mandelbrot set intersects the x,y axis.
	setx := -2.5
	sety := -1.0
	// width/height of the set.
	setw := 3.5
	seth := 2.0
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			// Scale in the range (-2.5,1.0) for x and (-1.0,1.0) for y.
			c := complex(float64(x)/float64(w)*setw+setx,
				float64(y)/float64(h)*seth+sety)
			z := 0i
			i := 0
			for ; cmplx.Abs(z) < 2 && i < maxi; i++ {
				z = cmplx.Pow(z, 2) + c
			}

			if i == maxi {
				// Point is bounded.
				img.Set(x, y, color.Black)
			} else {
				// Point escapes to infinity.
				img.Set(x, y, color.Transparent)
			}
		}
	}
	png.Encode(os.Stdout, img)
}