Example using 2D Simplex noise

tilegen.go

// Copyright 2012 by Sascha L. Teichmann. All rights reserved.
//
// Simple example how to use 2D Simplex noise.
// $ go get bitbucket.org/s_l_teichmann/simplexnoise
// $ go build tilegen.go
//
package main

import (
	"bitbucket.org/s_l_teichmann/simplexnoise"
	"flag"
	"fmt"
	"image"
	"image/color"
	"image/png"
	"log"
	"os"
)

// Simplex noise returns [-1, 1] so we scale it to [0, 255].
func to_gray(v float64) color.Gray {
	return color.Gray{uint8((v + 1.0) * 128.0)}
}

func main() {
	var (
		seed   int64
		size   int
		xofs   int
		yofs   int
		step   float64
		output string
	)

	flag.Int64Var(&seed, "seed", 1, "random seed")
	flag.IntVar(&size, "size", 64, "tile size")
	flag.IntVar(&xofs, "xofs", 0, "xofs")
	flag.IntVar(&yofs, "yofs", 0, "yofs")
	flag.Float64Var(&step, "step", 1.0/256.0, "step")
	flag.StringVar(&output, "output", "", "file to store the tile")

	flag.Parse()

	img := image.NewGray(image.Rect(0, 0, size, size))

	sn := simplexnoise.NewSimplexNoise(seed)

	y_pos := float64(yofs*size) * step
	x_start := float64(xofs*size) * step

	for y := 0; y < size; y++ {
		x_pos := x_start
		for x := 0; x < size; x++ {
			img.Set(x, y, to_gray(sn.Noise2D(x_pos, y_pos)))
			x_pos += step
		}
		y_pos += step
	}

	if output == "" {
		output = fmt.Sprintf("%d-%d.png", xofs, yofs)
	}

	file, err := os.Create(output)
	if err != nil {
		log.Printf("Cannot open '%s'", output)
		os.Exit(1)
	}
	defer file.Close()

	if err := png.Encode(file, img); err != nil {
		log.Printf("Encoding failed '%s'", err)
		os.Exit(1)
	}
}