add images.go (c782e6af) · Commits · blackheaven / tinygraphs

app-backend/images.go

0 → 100644

+85 −0

Original line number	Diff line number	Diff line
		package main

		import (
		"bytes"
		"encoding/base64"
		"html/template"
		"image"
		"image/color"
		"image/draw"
		"image/jpeg"
		"log"
		"net/http"
		"strconv"
		)

		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 redHandler(w http.ResponseWriter, r *http.Request) {
		m := image.NewRGBA(image.Rect(0, 0, 240, 240))
		blue := color.RGBA{255, 0, 0, 255}
		draw.Draw(m, m.Bounds(), &image.Uniform{blue}, image.ZP, draw.Src)

		var img image.Image = m
		writeImageWithTemplate(w, &img)
		}

		var ImageTemplate string = `<!DOCTYPE html>
		<html lang="en"><head><title>{{ .Title }}</title></head>
		<body><img src="data:image/jpg;base64,{{.Image}}"></body>`

		// writeImageWithTemplate encodes an image 'img' in jpeg format and writes it into ResponseWriter using a template.
		func writeImageWithTemplate(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")
		}

		str := base64.StdEncoding.EncodeToString(buffer.Bytes())
		var tmpl, _ = template.New("image").Parse(ImageTemplate)

		data := map[string]interface{}{"Image": str}
		tmpl.Execute(w, data)
		}

		// writeImage encodes an image 'img' in jpeg format and writes it into ResponseWriter.
		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")
		}
		}

app-backend/main.go

+1 −0

Original line number	Diff line number	Diff line
		@@ -13,6 +13,7 @@ func main() {
		http.HandleFunc("/black/", blackHandler)
		http.HandleFunc("/green/", greenHandler)
		http.HandleFunc("/blue/", blueHandler)
		http.HandleFunc("/red/", redHandler)
		http.Handle("/", http.FileServer(http.Dir(*root)))
		log.Println("Listening on " + os.Getenv("PORT"))
		err := http.ListenAndServe(":"+os.Getenv("PORT"), nil)