Resize a PNG image, optionally delineating individual pixels

resize.go

package main

import (
	"flag"
	"image"
	"image/color"
	"image/png"
	"log"
	"os"
)

var in = flag.String("in", "", "File to resize")
var x = flag.Int("x", 5, "Factor to resize")
var del = flag.Bool("d", false, "Whether to deliniate pixels")

func main() {
	flag.Parse()

	inf, err := os.Open(*in)
	if err != nil {
		log.Fatal(err)
	}
	i, err := png.Decode(inf)
	if err != nil {
		log.Fatal(err)
	}

	r := resized{i, *x, *del}
	newf, err := os.Create("big-" + *in)
	if err != nil {
		log.Fatal(err)
	}
	png.Encode(newf, r)
}

type resized struct {
	i         image.Image
	factor    int
	deliniate bool
}

func (r resized) ColorModel() color.Model {
	return r.i.ColorModel()
}

func (r resized) Bounds() image.Rectangle {
	return image.Rectangle{r.i.Bounds().Min, image.Point{
		X: r.i.Bounds().Max.X * r.factor,
		Y: r.i.Bounds().Max.Y * r.factor,
	}}
}

func (r resized) At(x, y int) color.Color {
	if r.deliniate && (x%r.factor == 0 || y%r.factor == 0) {
		return color.Gray{0}
	}
	return r.i.At(x/r.factor, y/r.factor)
}