Face Detection In Xamarin.Android

Vaikesh K P

6y36.2k12100Article

Xamarin Android XML Android AppFace Detection

12 Comments

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Mark Anderson5y ago
Will this also compile to run on ios?
muthu karunarathna9y ago
This is not working because camerabitmap is null always. So you need to set it as follow. protected override void OnActivityResult (int requestCode, Result resultCode, Intent data) { base.OnActivityResult (requestCode, resultCode, data); //check if method return takepicturecode Bitmap photo = (Bitmap)data.Extras.Get("data"); cameraBitmap = photo; if (TAKE_PICTURE_CODE == requestCode){ //Call a method to process image data processCameraImage(photo); } } Also you need to change the parameter in processCameraImage from intent to bitmap private void processCameraImage(Bitmap intent) { //Change layout to main Layout SetContentView(Resource.Layout.detectlayout); Button detect_face = FindViewById<Button> (Resource.Id.detect_face); detect_face.Click += detect_face_Clicked; ImageView image_view = FindViewById<ImageView> (Resource.Id.image_view); //Set image image_view.SetImageBitmap(intent); }
Arvind Chourasiya10y ago
Hello Vaikesh in second screen camera not opening.only button showing detect face after clicking that button nothing happening.It should open camera in second screen also or not?
Arthur Aricaya10y ago
thank for this..but when i clicked detect faces nothing happens...
Ankur Mistry10y ago
Very nice article
Banketeshvar Narayan10y ago
Nice Share
Praveen Kumar10y ago
Very Nice
Sibeesh Venu10y ago
Nice Share
Ankit Bansal10y ago
nice one..
Humayun Kabir Mamun10y ago
Nice...
Vaikesh K P10y ago
Thanks Santhakumar Munuswamy
Santhakumar Munuswamy10y ago
Good one

Firstly, we can create our main layout having a button to take a picture using camera and name it the following,

Main.axml

<?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="match_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 we need a layout named detectlayout.axml having an ImageView to display the picture which we had captured using camera and a Button to detect faces in that Image.

<?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_report_image" />
<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>

Now let's start coding.

Firstly, we want to open an activity to take a picture.

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

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

private void processCameraImage(Intent intent)
{
//Change layout to main Layout
SetContentView(Resource.Layout.detectlayout);
Button detect_face = FindViewById<Button> (Resource.Id.detect_face);
detect_face.Click += detect_face_Clicked;
ImageView image_view = FindViewById<ImageView> (Resource.Id.image_view);
//Set image
image_view.SetImageBitmap(cameraBitmap);
}

Add our main ingredient, here we detecting the faces on the picture and drawing a square to mark those faces.

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
FaceDetector.Face[] faces = new 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.Green;
//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 the stage is set for the show, only we need to do is just rearrange the code together in a logical way.

Go through the attachment for the complete project.