go x11 mpeg stream viewer

gistfile1.go

// X11 viewer for a MJPEG stream, such as the one obtained from the
// Android app https://market.android.com/details?id=com.pas.webcam

package main

import (
	"exp/gui/x11"
	"flag"
	"http"
	"image"
	"image/draw"
	"image/jpeg"
	"log"
	"mime"
	"mime/multipart"
	"strings"
)

var (
	stream = flag.String("stream", "http://10.0.0.212:8080/videofeed", "MJPEG stream")
	flush  = flag.Bool("flush", true, "flush x11 after each frame")
)

func main() {
	flag.Parse()
	res, err := http.Get(*stream)
	if err != nil {
		log.Fatalf("GET of %q: %v", *stream, err)
	}
	log.Printf("Content: %v", res.Header.Get("Content-Type"))

	_, params, err := mime.ParseMediaType(res.Header.Get("Content-Type"))
	if err != nil {
		log.Fatalf("ParseMediaType: %v", err)
	}
	boundary := params["boundary"]
	if !strings.HasPrefix(boundary, "--") {
		log.Fatalf("expected boundary to start with --, got %q", boundary)
	}
	r := multipart.NewReader(res.Body, boundary[2:])
	framec := make(chan image.Image, 10)
	go decodeFrames(framec, r)

	win, err := x11.NewWindow()
	if err != nil {
		log.Fatalf("NewWindow: %v", err)
	}

	eventc := win.EventChan()
	for {
		select {
		case evt, ok := <-eventc:
			if !ok {
				return
			}
			log.Printf("Event: %#v", evt)
		case im := <-framec:
			log.Printf("frame")
			sim := win.Screen()
			draw.Draw(sim, im.Bounds(), im, sim.Bounds().Min, draw.Over)
			if *flush {
				win.FlushImage()
			}
		}
	}
}

func decodeFrames(c chan image.Image, r *multipart.Reader) {
	for {
		p, err := r.NextPart()
		if err != nil {
			log.Fatalf("NextPart: %v", err)
		}
		im, err := jpeg.Decode(p)
		if err != nil {
			log.Fatalf("jpeg Decode: %v", err)
		}
		c <- im
	}
}