golang: Get image dimension

GetImageDimension.go

package main

import (
	"fmt"
	"image"
	_ "image/gif"
	_ "image/jpeg"
	_ "image/png"
	"io"
	"os"
)

func getImageDimension(r io.Reader) (int, int) {
	config, _, err := image.DecodeConfig(r)
	if err != nil {
		panic(err)
	}

	return config.Width, config.Height
}

func main() {
	f, err := os.Open("image-400x300.png")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	w, h := getImageDimension(f)
	fmt.Printf("Width: %d\nHeight: %d\n", w, h)
}