move image handles into separate file

package main

import (

	"bytes"

	"flag"

	"image"

	"image/color"

	"image/draw"

	"image/jpeg"

	"log"

	"net/http"

	"os"

	"strconv"

)

var root = flag.String("root", "app", "file system path")

		log.Fatal("ListenAndServe:", err)

	}

}

func blackHandler(w http.ResponseWriter, r *http.Request) {

	m := image.NewRGBA(image.Rect(0, 0, 240, 240))

	black := color.RGBA{0, 0, 0, 255}

	draw.Draw(m, m.Bounds(), &image.Uniform{black}, image.ZP, draw.Src)

	var img image.Image = m

	writeImage(w, &img)

}

func greenHandler(w http.ResponseWriter, r *http.Request) {

	// prepare

	m := image.NewRGBA(image.Rect(0, 0, 240, 240))

	green := color.RGBA{0, 128, 0, 255}

	draw.Draw(m, m.Bounds(), &image.Uniform{green}, image.ZP, draw.Src)

	var img image.Image = m

	writeImage(w, &img)

}

func blueHandler(w http.ResponseWriter, r *http.Request) {

	m := image.NewRGBA(image.Rect(0, 0, 240, 240))

	blue := color.RGBA{0, 0, 255, 255}

	draw.Draw(m, m.Bounds(), &image.Uniform{blue}, image.ZP, draw.Src)

	var img image.Image = m

	writeImage(w, &img)

}

func writeImage(w http.ResponseWriter, img *image.Image) {

	buffer := new(bytes.Buffer)

	if err := jpeg.Encode(buffer, *img, nil); err != nil {

		log.Fatalln("unable to encode image")

	}

	w.Header().Set("Content-Type", "image/jpeg")

	w.Header().Set("Content-Length", strconv.Itoa(len(buffer.Bytes())))

	if _, err := w.Write(buffer.Bytes()); err != nil {

		log.Fatalln("unable to write image")

	}

}