Golang : Activate web camera and broadcast out base64 encoded images




For this tutorial, we will learn how to activate web camera with Golang + OpenCV and stream out base64 encoded images via HTTP server. This tutorial is derived from the lesson that I use to teach my son on the subject of computer vision and Golang. It is based on the Go-OpenCV tutorial on activating web camera (https://github.com/lazywei/go-opencv/blob/master/samples/webcam.go).

The program will activate the web camera when you point your web browser to localhost:8080 and begin streaming out base64 encoded images. You will have to scroll down the see the new images. LOL! Good enough to get a 3 years old kid excited about computer vision.

Before you start.

go get github.com/lazywei/go-opencv

Here you go!


 package main

 import (
  "bytes"
  "encoding/base64"
  "fmt"
  "github.com/lazywei/go-opencv/opencv"
  "image/png"
  "net/http"
 )

 func broadcast(w http.ResponseWriter, r *http.Request) {
  webCamera := opencv.NewCameraCapture(0)

  if webCamera == nil {
 panic("Unable to open camera")
  }

  defer webCamera.Release()

  for {
 if webCamera.GrabFrame() {
 imgFrame := webCamera.RetrieveFrame(1)
 if imgFrame != nil {
 //fmt.Println(imgFrame.ImageSize())
 //fmt.Println(imgFrame.ToImage())

 // convert IplImage(Intel Image Processing Library)
 // to image.Image
 goImgFrame := imgFrame.ToImage()

 // and then convert to []byte
 // with the help of png.Encode() function

 frameBuffer := new(bytes.Buffer)
 //frameBuffer := make([]byte, imgFrame.ImageSize())
 err := png.Encode(frameBuffer, goImgFrame)

 if err != nil {
 panic(err)
 }

 // convert the buffer bytes to base64 string - use buf.Bytes() for new image
 imgBase64Str := base64.StdEncoding.EncodeToString(frameBuffer.Bytes())

 // Embed into an html without PNG file
 img2html := "<html><body><img src=\"data:image/png;base64," + imgBase64Str + "\" /></body></html>"

 w.Write([]byte(fmt.Sprintf(img2html)))

 // TODO :
 // encode frames to stream via WebRTC

 fmt.Println("Streaming....")

 }
 }
  }

 }

 func main() {
  fmt.Println("Broadcasting...")
  mux := http.NewServeMux()
  mux.HandleFunc("/", broadcast)
  http.ListenAndServe(":8080", mux)
 }

streaming out base64 encoded images to browser

streaming out base64 encoded images to browser


NOTES:

In case you get these error messages :

No package 'opencv' found

Package opencv was not found in the pkg-config search path.

Perhaps you should add the directory containing `opencv.pc'

to the PKGCONFIGPATH environment variable

Fix this problem by installing openCV.

On MacOSX :

>brew install homebrew/science/opencv

References:

https://github.com/lazywei/go-opencv/blob/master/opencv/goimage.go

https://www.socketloop.com/tutorials/golang-how-to-stream-file-to-client-browser-or-write-to-http-responsewriter

https://www.socketloop.com/references/golang-net-http-servecontent-function-example

http://stackoverflow.com/questions/35667501/golang-seeking-through-a-video-serving-as-bytes

  See also : Golang : Save webcamera frames to video file



Tags : golang go-openCV web-camera streaming-images base64

Adam Ng By Adam Ng

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