Face detection API implementation

Face detection API is used to detect human faces automatically from media files such as images & video. I have developed an application which detects faces photo taken from device Camera and gallery images as well.

Step 1: Add camera permission & face detection metadata in manifest

<uses-feature android:name="android.hardware.camera" android:required="true" />
<uses-feature android:name="android.hardware.camera.autofocus" />


<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

<meta-data    android:name="com.google.android.gms.vision.DEPENDENCIES"    android:value="face" />

Step 2: Checking camera & external storage for gallery permission 

ActivityCompat.requestPermissions(this,
        new String[]{Manifest.permission.CAMERA},
        CAMERA_PERMISSION_REQUEST_CODE);

ActivityCompat.requestPermissions(this,
        new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
        GALLERY_PERMISSION_REQUEST_CODE);

Step 3: Custom camera activity using SurfaceView

We have to initialize surface view in OnCreate() then get surface holder from surface view and add callbacks,

surfaceView = (SurfaceView)findViewById(R.id.camerapreview);
surfaceHolder = surfaceView.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

We have to start camera preview in surfaceChanged() callback method and then open a camera from surfaceCreated() callback.

@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width,
                           int height) {
    // TODO Auto-generated method stub    if(previewing){
        camera.stopPreview();
        previewing = false;
    }

    if (camera != null){
        try {
            int rotation=setCameraDisplayOrientation(AndroidCamera.this,
                    Camera.CameraInfo.CAMERA_FACING_FRONT,camera);
            camera.setDisplayOrientation(rotation);
            camera.setPreviewDisplay(surfaceHolder);
            camera.startPreview();
            previewing = true;
        } catch (IOException e) {
            // TODO Auto-generated catch block            e.printStackTrace();
        }
    }
}

@Overridepublic void surfaceCreated(SurfaceHolder holder) {
    // TODO Auto-generated method stub    camera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);        
}

Step 4: To avoid mirror camera imaging
Set camera orientation based on Surface rotation. 

android.hardware.Camera.CameraInfo info =
        new android.hardware.Camera.CameraInfo();

android.hardware.Camera.getCameraInfo(cameraId, info);
int rotation = activity.getWindowManager().getDefaultDisplay()
        .getRotation();
int degrees = 0;
switch (rotation) {
    case Surface.ROTATION_0: degrees = 0; break;
    case Surface.ROTATION_90: degrees = 90; break;
    case Surface.ROTATION_180: degrees = 180; break;
    case Surface.ROTATION_270: degrees = 270; break;
}

int result;
if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
    result = (info.orientation + degrees) % 360;
    result = (360 - result) % 360;  
} else {
    result = (info.orientation - degrees + 360) % 360;
}

Step 5: Take picture & Save image
calling takePicture method & image byte data return to myPictureCallback.

camera.takePicture(myShutterCallback,
        myPictureCallback_RAW, myPictureCallback_JPG);

fileUserPhoto = new File(dir.getAbsolutePath(), "pic.png");
try {
    fileUserPhoto.createNewFile();
}catch (IOException ex){
    Log.e(TAG,"IOException:"+ex.getLocalizedMessage());
}

try {
    FileOutputStream fileOS=new FileOutputStream(fileUserPhoto);
    android.hardware.Camera.CameraInfo info =
            new android.hardware.Camera.CameraInfo();
    android.hardware.Camera.getCameraInfo(Camera.CameraInfo.CAMERA_FACING_FRONT, info);

    int rotation=setCameraDisplayOrientation(AndroidCamera.this,Camera.CameraInfo.CAMERA_FACING_FRONT,camera);
    rotation=rotation+180;

    Bitmap realImage= BitmapFactory.decodeByteArray(imageByte,0,imageByte.length);
    Bitmap bitmap= rotate(realImage,rotation);

    boolean isSaved=bitmap.compress(Bitmap.CompressFormat.JPEG,100,fileOS);
    Log.d(TAG,"saveCameraImage:"+isSaved);
    fileOS.close();
    setResult(RESULT_OK);
    finish();
} catch (FileNotFoundException e) {
    // TODO Auto-generated catch block    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block    e.printStackTrace();
}

Step 6: Detecting face from FaceOverlayView

FaceDetector detector = new FaceDetector.Builder( getContext() )
        .setTrackingEnabled(false)
        .build();
if (!detector.isOperational()) {
    Toast.makeText(getContext(), "Face detection error.", Toast.LENGTH_LONG).show();
} else {
    Frame frame = new Frame.Builder().setBitmap(bitmap).build();
    mFaces = detector.detect(frame);
    detector.release();
}
invalidate();

Once the face is detected, the image bitmap is added to the overlay frame view. 

Step 7: Drawing face box over the taken photo
The paint should be defined as a member variable rather than being created on each onDraw request, but left here for emphasis.

Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(5);

float left = 0;
float top = 0;
float right = 0;
float bottom = 0;

for( int i = 0; i < mFaces.size(); i++ ) {
    Face face = mFaces.valueAt(i);

    left = (float) ( face.getPosition().x * scale );
    top = (float) ( face.getPosition().y * scale );
    right = (float) scale * ( face.getPosition().x + face.getWidth() );
    bottom = (float) scale * ( face.getPosition().y + face.getHeight() );

    canvas.drawRect( left, top, right, bottom, paint );
}

<com.truedreamz.facedetection.FaceOverlayView
    android:id="@+id/imgPhoto"
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    android:layout_margin="2dp"
    android:layout_gravity="center_horizontal"
    android:scaleType="fitXY"
    />

Add FaceOverlayView to the main layout of application and assign taken photos or selected picture from gallery i.e picking images using intent.

I have uploaded the full source code in Github for reference,
https://github.com/JayaprakashR-Zealot/Knowledge-Circle---Android/tree/master/FaceDetection


Happy Coding !!!
Thanks!!!