Face Detect


This is a more complete example that opens a video capture device using device “0”. It also uses the CascadeClassifier class to load an external data file containing the classifier data. The program grabs each frame from the video, then uses the classifier to detect faces. If any faces are found, it draws a green rectangle around each one, then displays the video in an output window:

package main

import (


func main() {
	deviceID := 0

	// open webcam
	webcam, err := gocv.VideoCaptureDevice(int(deviceID))
	if err != nil {
		fmt.Printf("error opening video capture device: %v\n", deviceID)
	defer webcam.Close()

	// open display window
	window := gocv.NewWindow("Face Detect")
	defer window.Close()

	// prepare image matrix
	img := gocv.NewMat()
	defer img.Close()

	// color for the rect when faces detected
	blue := color.RGBA{0, 0, 255, 0}

	// load classifier to recognize faces
	classifier := gocv.NewCascadeClassifier()
	defer classifier.Close()

	fmt.Printf("start reading camera device: %v\n", deviceID)
	for {
		if ok := webcam.Read(img); !ok {
			fmt.Printf("cannot read device %d\n", deviceID)
		if img.Empty() {

		// detect faces
		rects := classifier.DetectMultiScale(img)
		fmt.Printf("found %d faces\n", len(rects))

		// draw a rectangle around each face on the original image
		for _, r := range rects {
			gocv.Rectangle(img, r, blue, 3)

		// show the image in the window, and wait 1 millisecond