Facial Detection with Xamarin.Android

hey hooo¡¡¡¡¡ today we work with the Face Detection Android's Api its very easy to use and a great tool

First, create a new Android Ice Cream Sandwich app because Face Detection Api only works with Android 4 and above:

In the Main Layout put a TextView and a Button

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dip">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Click Take a Picture button"
        android:gravity="center_horizontal"
        android:layout_weight="1.0" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/take_picture"
        android:layout_margin="5dip"
        android:text="Take Picture"
        android:layout_gravity="center_horizontal" />
</LinearLayout>

Now creates a new layout(detectlayout.axml) and put a imageview and a button

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <ImageView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/image_view"
        android:layout_weight="1.0"
        android:src="@android:drawable/ic_menu_close_clear_cancel" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/detect_face"
        android:text="Detect Face"
        android:layout_gravity="center_horizontal" />
</LinearLayout>

In the MainActivity.cs puts that code and it all now you app can uses facial detection android api:

using Android.Graphics;
using Android.Media;
using System.IO;

[Activity (Label = "FacialDetection", MainLauncher = true, ScreenOrientation = Android.Content.PM.ScreenOrientation.Portrait)]
 public class MainActivity : Activity
 {
  //Intent code for camera activity
  private static int TAKE_PICTURE_CODE = 100;
  //Max Faces to detect in a picture
  private static int MAX_FACES = 5;
  //Bitmap of a picture taken
  private Bitmap cameraBitmap = null;

  protected override void OnCreate (Bundle savedInstanceState)
  {
   base.OnCreate (savedInstanceState);
   //Set main layout
   SetContentView (Resource.Layout.Main);
   //set click event for take picture button
   ((Button)FindViewById(Resource.Id.take_picture)).Click += btntake_HandleClick;
  }

  //Take Picture click event
  void btntake_HandleClick (object sender, EventArgs e)
  {
   //call OpenCamera() Event
   openCamera();
  }

  //OnActivityResult
  protected override void OnActivityResult (int requestCode, Result resultCode, Intent data)
  {
   base.OnActivityResult (requestCode, resultCode, data);
   //check if method return takepicturecode
   if(TAKE_PICTURE_CODE == requestCode){
    //Call a method to process image data
    processCameraImage(data);
   }
  }

  /// <summary>
  /// Open an activity for take a picture
  /// </summary>
  private void openCamera(){
   Intent intent = new Intent(Android.Provider.MediaStore.ActionImageCapture);
   StartActivityForResult (intent, TAKE_PICTURE_CODE);
  }

  /// <summary>
  /// Process picture taken an change UI to detect face
  /// </summary>
  /// <param name="intent">Intent.</param>
  private void processCameraImage(Intent intent){
   //Changue main layout for detect layout
   SetContentView (Resource.Layout.detectlayout);

   //set click event for face detect button
   ((Button)FindViewById(Resource.Id.detect_face)).Click += btnDetect_HandleClick;

   //get imageview from layout
   ImageView imageView = (ImageView)FindViewById(Resource.Id.image_view);


   //put picture to CameraBitmap Variable
   cameraBitmap = (Bitmap)intent.Extras.Get("data");

   //set image from CameraBitmap
   imageView.SetImageBitmap(cameraBitmap);
  }

  //Detect Faces Click Event
  void btnDetect_HandleClick (object sender, EventArgs e)
  {
   //Call detectFaces() method
   detectFaces();
  }

  /// <summary>
  /// detect faces on a picture and draw a square in each face
  /// </summary<
  private void detectFaces(){
   //first check if picture has been taken
   if(null != cameraBitmap){
    //get width of a picture
    int width = cameraBitmap.Width;
    //get height of a picture
    int height = cameraBitmap.Height;
    //Initialize a facedetector with the picture dimensions and the max number of faces to check
    FaceDetector detector = new FaceDetector(width, height, MainActivity.MAX_FACES);
    //Create an array of faces with the number of max faces to check
    Android.Media.FaceDetector.Face[] faces = new Android.Media.FaceDetector.Face[MainActivity.MAX_FACES];

    //create a main bitmap
    Bitmap bitmap565 = Bitmap.CreateBitmap(width, height, Bitmap.Config.Rgb565);
    //create a dither paint
    Paint ditherPaint = new Paint();
    //create a draw paint
    Paint drawPaint = new Paint();

    //set true dither to dither paint variable
    ditherPaint.Dither = true;
    //set color red for the square
    drawPaint.Color = Color.Red;
    //set stroke to style
    drawPaint.SetStyle(Paint.Style.Stroke);
    //set stroke width
    drawPaint.StrokeWidth = 2;

    //Create a canvas
    Canvas canvas = new Canvas();
    //set bitmap to canvas
    canvas.SetBitmap(bitmap565);
    //draw bitmap to canvas
    canvas.DrawBitmap(cameraBitmap, 0, 0, ditherPaint);

    //get a number of faces detected
    int facesFound = detector.FindFaces(bitmap565, faces);
    //mid face point
    PointF midPoint = new PointF();
    //eye distance variable
    float eyeDistance = 0.0f;
    //confidence variable
    float confidence = 0.0f;
    //print numbre of faces found
    System.Console.WriteLine ("Number of faces found: " + facesFound);

    //check if found at least one face
    if(facesFound > 0)
    {
     //for each face draw a red squeare
     for(int index=0; index<facesFound; ++index){
      // get midpoint of a face
      faces[index].GetMidPoint(midPoint);
      //get eye distance
      eyeDistance = faces[index].EyesDistance();
      //get confidence
      confidence = faces [index].Confidence ();
      //print all parameters
      System.Console.WriteLine ("Confidence: " + confidence + 
       ", Eye distance: " + eyeDistance + 
       ", Mid Point: (" + midPoint.X + ", " + midPoint.Y + ")");
      //draw a square in the picture
      canvas.DrawRect((int)midPoint.X - eyeDistance , 
       (int)midPoint.Y- eyeDistance , 
       (int)midPoint.X + eyeDistance, 
       (int)midPoint.Y + eyeDistance, drawPaint);
     }
    }

    //get imageview from layout
    ImageView imageView = (ImageView)FindViewById(Resource.Id.image_view);
    //set image with the red squares to imageview
    imageView.SetImageBitmap(bitmap565);
   }
  }
 }

Now you can take pictures and check how many faces found it

Full Example GitHub: https://github.com/AlejandroRuiz/Mono/tree/master/FacialDetection

That's it, you are awesome a tiny god, now take a break and wait for the next entry.