Examples for image copying and GIF exploding in Go

cp.go

package main

import (
	"flag"
	"io"
	"log"
	"os"
)

var (
	src = flag.String("src", "", "Source file")
	dst = flag.String("dst", "", "Destination file")
)

func main() {
	flag.Parse()

	// Open the source file
	s, err := os.Open(*src)
	if err != nil {
		log.Fatal(err)
	}
	defer s.Close()

	// Create a destination file
	d, err := os.Create(*dst)
	if err != nil {
		log.Fatal(err)
	}
	defer d.Close()

	// Copy all the bytes from s into d
	_, err = io.Copy(d, s)
	if err != nil {
		log.Fatal(err)
	}
}

cppng.go

// Reads a PNG image and copies its pixels to a new PNG image.
package main

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

var (
	src = flag.String("src", "", "Source file")
)

func main() {
	flag.Parse()

	// Open the source file
	s, err := os.Open(*src)
	if err != nil {
		log.Fatal(err)
	}
	defer s.Close()

	// Decode the source file as a PNG
	simg, err := png.Decode(s)
	if err != nil {
		log.Fatal(err)
	}

	// Create a new RGBA image with the same bounds as simg
	dimg := image.NewRGBA(image.Rectangle{
		simg.Bounds().Min,
		simg.Bounds().Max,
	})

	// For each pixel in simg, set that pixel on dimg
	for x := simg.Bounds().Min.X; x < simg.Bounds().Max.X; x++ {
		for y := simg.Bounds().Min.Y; y < simg.Bounds().Max.Y; y++ {
			dimg.Set(x, y, simg.At(x, y))
		}
	}

	// Create a destination file
	d, err := os.Create(fmt.Sprintf("%s_copy.png", *src))
	if err != nil {
		log.Fatal(err)
	}
	defer d.Close()

	// Write the new image to the destination file
	err = png.Encode(d, dimg)
	if err != nil {
		log.Fatal(err)
	}
}

explodegif.go

// Reads the each frame of a GIF image and writes it to a new file as PNG.
package main

import (
	"flag"
	"fmt"
	"image"
	"image/gif"
	"image/png"
	"log"
	"os"
)

var (
	src = flag.String("src", "", "Source file")
)

func main() {
	flag.Parse()

	// Open the source file
	s, err := os.Open(*src)
	if err != nil {
		log.Fatal(err)
	}
	defer s.Close()

	// Decode the source file as a GIF
	// DecodeAll reads all frames of the GIF
	simg, err := gif.DecodeAll(s)
	if err != nil {
		log.Fatal(err)
	}

	for i, frame := range simg.Image {
		// Create a new RGBA image with the same bounds as frame
		dimg := image.NewRGBA(image.Rectangle{
			frame.Bounds().Min,
			frame.Bounds().Max,
		})

		// For each pixel in frame, set that pixel on dimg
		for x := frame.Bounds().Min.X; x < frame.Bounds().Max.X; x++ {
			for y := frame.Bounds().Min.Y; y < frame.Bounds().Max.Y; y++ {
				dimg.Set(x, y, frame.At(x, y))
			}
		}

		// Create a destination file
		d, err := os.Create(fmt.Sprintf("%s_%d.png", *src, i))
		if err != nil {
			log.Fatal(err)
		}
		defer d.Close()

		// Write the new image to the destination file
		err = png.Encode(d, dimg)
		if err != nil {
			log.Fatal(err)
		}
	}
}