Added a sample for face detection on video from builtin camera

samples/webcam_facedetect.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path"
+
+	"github.com/lazywei/go-opencv/opencv"
+)
+
+func main() {
+	win := opencv.NewWindow("Go-OpenCV Webcam Face Detection")
+	defer win.Destroy()
+
+	cap := opencv.NewCameraCapture(0)
+	if cap == nil {
+		panic("cannot open camera")
+	}
+	defer cap.Release()
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		panic(err)
+	}
+	cascade := opencv.LoadHaarClassifierCascade(path.Join(cwd, "haarcascade_frontalface_alt.xml"))
+
+	fmt.Println("Press ESC to quit")
+	for {
+		if cap.GrabFrame() {
+			img := cap.RetrieveFrame(1)
+			if img != nil {
+				faces := cascade.DetectObjects(img)
+				for _, value := range faces {
+					opencv.Circle(img,
+						opencv.Point{
+							value.X() + (value.Width() / 2),
+							value.Y() + (value.Height() / 2),
+						},
+						value.Width()/2,
+						opencv.ScalarAll(255.0), 1, 1, 0)
+				}
+
+				win.ShowImage(img)
+			} else {
+				fmt.Println("nil image")
+			}
+		}
+		key := opencv.WaitKey(1)
+
+		if key == 27 {
+			os.Exit(0)
+		}
+	}
+}