无法在Android中使用FaceDetector检测到脸部

Question

I need to detect the user face and also compare the face to authenticate my application,for that I used FaceDetector API to detect the user face.

When i run my code it works without any defects.But it gives detected faces count as Zero.

    public class AndroidFaceDetectorActivity extends Activity {
    private static final int TAKE_PICTURE_CODE = 100;
    private static final int MAX_FACES = 5;

    private Bitmap cameraBitmap = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ((Button)findViewById(R.id.take_picture)).setOnClickListener(btnClick);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);

            if(TAKE_PICTURE_CODE == requestCode){
                    processCameraImage(data);
            }
    }


    private void openCamera(){
        Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);

        startActivityForResult(intent, TAKE_PICTURE_CODE);
    }

    private void processCameraImage(Intent intent){
        setContentView(R.layout.detectlayout);

        ((Button)findViewById(R.id.detect_face)).setOnClickListener(btnClick);

        ImageView imageView = (ImageView)findViewById(R.id.image_view);

        cameraBitmap = (Bitmap)intent.getExtras().get("data");

        imageView.setImageBitmap(cameraBitmap);
    }

    private void detectFaces(){
        if(null != cameraBitmap){
                Log.d("FACE_RECOGNITION","CHECK");
                int width = cameraBitmap.getWidth();
                int height = cameraBitmap.getHeight();

                FaceDetector detector = new FaceDetector(width, height,AndroidFaceDetectorActivity.MAX_FACES);
                Face[] faces = new Face[AndroidFaceDetectorActivity.MAX_FACES];

                Bitmap bitmap565 = Bitmap.createBitmap(width, height, Config.RGB_565);
                Paint ditherPaint = new Paint();
                Paint drawPaint = new Paint();

                ditherPaint.setDither(true);
                drawPaint.setColor(Color.RED);
                drawPaint.setStyle(Paint.Style.STROKE);
                drawPaint.setStrokeWidth(2);

                Canvas canvas = new Canvas();
                canvas.setBitmap(bitmap565);
                canvas.drawBitmap(cameraBitmap, 0, 0, ditherPaint);

                int facesFound = detector.findFaces(bitmap565, faces);
                PointF midPoint = new PointF();
                float eyeDistance = 0.0f;
                float confidence = 0.0f;

                Log.i("FaceDetector", "Number of faces found: " + facesFound);

                if(facesFound > 0)
                {
                        for(int index=0; index<facesFound; ++index){
                                faces[index].getMidPoint(midPoint);
                                eyeDistance = faces[index].eyesDistance();
                                confidence = faces[index].confidence();

                                Log.i("FaceDetector", 
                                                "Confidence: " + confidence + 
                                                ", Eye distance: " + eyeDistance + 
                                                ", Mid Point: (" + midPoint.x + ", " + midPoint.y + ")");

                                canvas.drawRect((int)midPoint.x - eyeDistance , 
                                                                (int)midPoint.y - eyeDistance , 
                                                                (int)midPoint.x + eyeDistance, 
                                                                (int)midPoint.y + eyeDistance, drawPaint);
                        }
                }

                String filepath = Environment.getExternalStorageDirectory() + "/facedetect" + System.currentTimeMillis() + ".jpg";

                    try {
                            FileOutputStream fos = new FileOutputStream(filepath);

                            bitmap565.compress(CompressFormat.JPEG, 90, fos);

                            fos.flush();
                            fos.close();
                    } catch (FileNotFoundException e) {
                            e.printStackTrace();
                    } catch (IOException e) {
                            e.printStackTrace();
                    }

                    ImageView imageView = (ImageView)findViewById(R.id.image_view);

                    imageView.setImageBitmap(bitmap565);
        }
    }

    private View.OnClickListener btnClick = new View.OnClickListener() {
            //@Override
            public void onClick(View v) {
                    switch(v.getId()){
                            case R.id.take_picture:         openCamera();   break;
                            case R.id.detect_face:          detectFaces();  break;  
                    }
            }
    };
}

What i did wrong?

or

Is any other way to do that?

Thanks

Answer 1

getExtras().get("data") for MediaStore.ACTION_IMAGE_CAPTURE intent produces very low-resolution bitmap (I believe it's 160x120 px) which could work as a thumbnail, but is not enough for face detection to do its job.

Normally face detection is OK on medium-res images (eg 64x480 px) that you can receive form Camera.previewCallback() , but this way you need permissions and code that controls the camera in your app, you cannot use an intent for that.

Here is the official into to face detection on Android: http://developer.android.com/guide/topics/media/camera.html#face-detection .

If you really prefer it this way, you may use getData() to find the captured image at its full resolution, and convert it into a bitmap, like

cameraBitmap = BitmapFactory.decodeFile(data.getData().getPath());