Face Detection In Xamarin.Android

First we can create our main layout having a button to take picture using camera and name it as:

Main.axml

1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:orientation="vertical"  
4.     android:layout_width="fill_parent"  
5.     android:layout_height="match_parent"  
6.     android:padding="10dip">  
7.     <TextView  
8.         android:layout_width="fill_parent"  
9.         android:layout_height="wrap_content"  
10.         android:text="Click Take a Picture button"  
11.         android:gravity="center_horizontal"  
12.         android:layout_weight="1.0" />  
13.     <Button  
14.         android:layout_width="wrap_content"  
15.         android:layout_height="wrap_content"  
16.         android:id="@+id/take_picture"  
17.         android:layout_margin="5dip"  
18.         android:text="Take Picture"  
19.         android:layout_gravity="center_horizontal" />  
20. </LinearLayout>   

Now we need a layout named detectlayout.axml having a ImageView to display the picture which we had captured using camera and a Button to detect faces in that Image.

1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:orientation="vertical"  
4.     android:layout_width="fill_parent"  
5.     android:layout_height="fill_parent">  
6.     <ImageView  
7.         android:layout_width="fill_parent"  
8.         android:layout_height="fill_parent"  
9.         android:id="@+id/image_view"  
10.         android:layout_weight="1.0"  
11.         android:src="@android:drawable/ic_menu_report_image" />  
12.     <Button  
13.         android:layout_width="wrap_content"  
14.         android:layout_height="wrap_content"  
15.         android:id="@+id/detect_face"  
16.         android:text="Detect Face"  
17.         android:layout_gravity="center_horizontal" />  
18. </LinearLayout>   

Now let's start coding.

First we want to open an activity to take picture.

1. private void openCamera()  
2. {  
3.    Intent intent = new Intent (Android.Provider.MediaStore.ActionImageCapture);  
4.    StartActivityForResult (intent, TAKE_PICTURE_CODE);  
5. }   

Now we want to Process the captured picture and display it on the detectlayout.axml.

1. private void processCameraImage(Intent intent)  
2. {  
3.     //Change layout to main Layout  
4.     SetContentView(Resource.Layout.detectlayout);  
5.   
6.     Button detect_face = FindViewById<Button> (Resource.Id.detect_face);  
7.   
8.     detect_face.Click += detect_face_Clicked;  
9.   
10.     ImageView image_view = FindViewById<ImageView> (Resource.Id.image_view);  
11.   
12.     //Set image   
13.     image_view.SetImageBitmap(cameraBitmap);  
14. }   

Now we are going to add our main ingredient, here we detecting the faces on the picture and drawing a square to mark those faces.

1. private void detectFaces(){  
2.     //first check if picture has been taken  
3.     if(null != cameraBitmap){  
4.         //get width of a picture  
5.         int width = cameraBitmap.Width;  
6.         //get height of a picture  
7.         int height = cameraBitmap.Height;  
8.         //Initialize a facedetector with the picture dimensions and the max number of faces to check  
9.         FaceDetector detector = new FaceDetector(width, height, MainActivity.MAX_FACES);  
10.         //Create an array of faces with the number of max faces to check  
11.         FaceDetector.Face[] faces = new FaceDetector.Face[MainActivity.MAX_FACES];  
12.   
13.         //create a main bitmap  
14.         Bitmap bitmap565 = Bitmap.CreateBitmap(width, height, Bitmap.Config.Rgb565);  
15.         //create a dither paint  
16.         Paint ditherPaint = new Paint();  
17.         //create a draw paint  
18.         Paint drawPaint = new Paint();  
19.   
20.         //set true dither to dither paint variable  
21.         ditherPaint.Dither = true;  
22.         //set color red for the square  
23.         drawPaint.Color = Color.Green;  
24.         //set stroke to style  
25.         drawPaint.SetStyle(Paint.Style.Stroke);  
26.         //set stroke width  
27.         drawPaint.StrokeWidth = 2;  
28.   
29.         //Create a canvas  
30.         Canvas canvas = new Canvas();  
31.         //set bitmap to canvas  
32.         canvas.SetBitmap(bitmap565);  
33.         //draw bitmap to canvas  
34.         canvas.DrawBitmap(cameraBitmap, 0, 0, ditherPaint);  
35.   
36.         //get a number of faces detected  
37.         int facesFound = detector.FindFaces(bitmap565, faces);  
38.         //mid face point  
39.         PointF midPoint = new PointF();  
40.         //eye distance variable  
41.         float eyeDistance = 0.0f;  
42.         //confidence variable  
43.         float confidence = 0.0f;  
44.         //print numbre of faces found  
45.         System.Console.WriteLine ("Number of faces found: " + facesFound);  
46.   
47.         //check if found at least one face  
48.         if(facesFound > 0)  
49.         {  
50.             //for each face draw a red squeare  
51.             for(int index=0; index<facesFound; ++index){  
52.                 // get midpoint of a face  
53.                 faces[index].GetMidPoint(midPoint);  
54.                 //get eye distance  
55.                 eyeDistance = faces[index].EyesDistance();  
56.                 //get confidence  
57.                 confidence = faces [index].Confidence ();  
58.                 //print all parameters  
59.                 System.Console.WriteLine ("Confidence: " + confidence +   
60.                     ", Eye distance: " + eyeDistance +   
61.                     ", Mid Point: (" + midPoint.X + ", " + midPoint.Y + ")");  
62.                 //draw a square in the picture  
63.                 canvas.DrawRect((int)midPoint.X - eyeDistance ,   
64.                     (int)midPoint.Y- eyeDistance ,   
65.                     (int)midPoint.X + eyeDistance,   
66.                     (int)midPoint.Y + eyeDistance, drawPaint);  
67.             }  
68.         }  
69.   
70.         //get imageview from layout  
71.         ImageView imageView = (ImageView)FindViewById(Resource.Id.image_view);  
72.         //set image with the red squares to imageview  
73.         imageView.SetImageBitmap(bitmap565);  
74.     }  
75. }   

Now the stage is set for the show, only we need to do is just rearrange the code together in a logical way. 


Click here to view the complete source code in GitHub Repo.

HAPPY CODING   (-_-)