Android setFocusArea and Auto Focus

Question

I've been battling with this feature for couple of days now...

It seems, that camera is ignoring(?) focus areas that I've defined. Here is snippets of the code:

Focusing:

protected void focusOnTouch(MotionEvent event) {
    if (camera != null) {
        Rect rect = calculateFocusArea(event.getX(), event.getY());

        Parameters parameters = camera.getParameters();
        parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);
        parameters.setFocusAreas(Lists.newArrayList(new Camera.Area(rect, 500)));

        camera.setParameters(parameters);
        camera.autoFocus(this);
    }
}

Focus area calculation:

private Rect calculateFocusArea(float x, float y) {
    int left = clamp(Float.valueOf((x / getSurfaceView().getWidth()) * 2000 - 1000).intValue(), focusAreaSize);
    int top = clamp(Float.valueOf((y / getSurfaceView().getHeight()) * 2000 - 1000).intValue(), focusAreaSize);

    return new Rect(left, top, left + focusAreaSize, top + focusAreaSize);
}

Couple of log events from Camera.AutoFocusCallback#onAutoFocus

Log.d(TAG, String.format("Auto focus success=%s. Focus mode: '%s'. Focused on: %s", focused, camera.getParameters().getFocusMode(), camera.getParameters().getFocusAreas().get(0).rect.toString()));

08-27 11:19:42.240: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-109, 643 - -13, 739)
08-27 11:19:55.514: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(20, 457 - 116, 553)
08-27 11:19:58.037: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-159, 536 - -63, 632)
08-27 11:20:00.129: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-28, 577 - 68, 673)

Visually it looks like focus succeeds on logged area, but the suddenly it loses focus and focus on center (0, 0), or what takes bigger part of SurfaceView is obtained.

focusAreaSize used in calculation is about 210px (96dp). Testing on HTC One where Camera.getParameters().getMaxNumFocusAreas() is 1.

Initial focus mode (before first tap) is set to FOCUS_MODE_CONTINUOUS_PICTURE.

Am I doing something wrong here? Tinkering with Camera.Area rectangle size or weight doesn't show any noticeable effect.

Martynas Jurkus · Accepted Answer · 2014-02-27T21:01:28.463

54

My problem was much simpler :)

All I had to do is cancel previously called autofocus. Basically the correct order of actions is this:

protected void focusOnTouch(MotionEvent event) {
    if (camera != null) {

        camera.cancelAutoFocus();
        Rect focusRect = calculateTapArea(event.getX(), event.getY(), 1f);
        Rect meteringRect = calculateTapArea(event.getX(), event.getY(), 1.5f);

        Parameters parameters = camera.getParameters();
        parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);
        parameters.setFocusAreas(Lists.newArrayList(new Camera.Area(focusRect, 1000)));

        if (meteringAreaSupported) {
            parameters.setMeteringAreas(Lists.newArrayList(new Camera.Area(meteringRect, 1000)));
        }

        camera.setParameters(parameters);
        camera.autoFocus(this);
    }
}

Update

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    ...
    Parameters p = camera.getParameters();
    if (p.getMaxNumMeteringAreas() > 0) {
       this.meteringAreaSupported = true;
    }
    ...
}

/**
 * Convert touch position x:y to {@link Camera.Area} position -1000:-1000 to 1000:1000.
 */
private Rect calculateTapArea(float x, float y, float coefficient) {
    int areaSize = Float.valueOf(focusAreaSize * coefficient).intValue();

    int left = clamp((int) x - areaSize / 2, 0, getSurfaceView().getWidth() - areaSize);
    int top = clamp((int) y - areaSize / 2, 0, getSurfaceView().getHeight() - areaSize);

    RectF rectF = new RectF(left, top, left + areaSize, top + areaSize);
    matrix.mapRect(rectF);

    return new Rect(Math.round(rectF.left), Math.round(rectF.top), Math.round(rectF.right), Math.round(rectF.bottom));
}

private int clamp(int x, int min, int max) {
    if (x > max) {
        return max;
    }
    if (x < min) {
        return min;
    }
    return x;
}

edited Feb 27 '14 at 21:01

answered Oct 09 '13 at 12:34

Martynas Jurkus

9,231
13
59
101

1

How did you get meteringAreaSupported? tx – MatheusJardimB Feb 27 '14 at 16:55
calculateTapArea is missing too :/ – MatheusJardimB Feb 27 '14 at 17:18
Thanks! I'll try it out. I'd give a second +1 for the attention :D – MatheusJardimB Feb 27 '14 at 21:05
Awesome! the code works pretty fine. I'd ask one more thing to complete your answer: how did you find those values to `focusAreaSize`. I mean, is there any documentation? Experimentation? – MatheusJardimB Feb 28 '14 at 12:54
2

Just experimentation. I used `72dp` for my size. – Martynas Jurkus Feb 28 '14 at 13:53
Thanks!! A tip: there is a RectF.round(Rect dst) to do the float -> int conversion – X.Y. Jun 10 '14 at 15:15
thanks, but I think the coordinate conversion is problematic, the related code inside the question is correct. Any thoughts? – dumbfingers Apr 09 '15 at 16:57
hi, excuse me but what is "matrix" variable? – Hugo Apr 22 '15 at 08:45
1

@Hugo Here is the full code for that: https://gist.github.com/mjurkus/21f7b9aa9b27a7661184 – Martynas Jurkus Apr 27 '15 at 11:16
@MartynasJurkus Why do you need to store meteringAreaSupported in a seperate field instead of just checking size of getMaxNumMeteringAreas when you get the parameters? – Greg Ennis May 15 '15 at 02:47
1

Thanks for your post! How do you ensure that the tapping area will be between -1000/1000 ? Shouldn't those values be clamped before creating the Rect ? – gbero Jan 07 '16 at 11:29
What should I use or set focusareasize to? What's recommended? – Euridice01 Nov 30 '16 at 21:54
@MartynasJurkus why do you need surfaceChanged()? – Euridice01 Dec 07 '16 at 19:23
Well, solution from what I have now and what is posted changed a bit. Now I'm starting preview or releasing camera there if activity is no longer active. – Martynas Jurkus Dec 08 '16 at 06:58
@MartynasJurkus If I wanted to set a fixed focus area with focus originating from the centerpoint... is that similar to your CalculateTapArea method? – Euridice01 Dec 13 '16 at 16:02
@Euridice01 yes – Martynas Jurkus Dec 14 '16 at 07:55
what is matrix in calculateTapArea method? – Hitesh Sarsava May 04 '18 at 08:06
instance of `android.graphics.Matrix` – Martynas Jurkus May 04 '18 at 11:35
what is ocusAreaSize in calculateTapArea method? – Amanpal Singh Jun 21 '18 at 17:52
It's just the size of are you want to be in pixels. Define a resource for example in integers.xml and load it as needed. – Martynas Jurkus Jun 22 '18 at 05:05
hi, i wonder that what is the parameters **weight** inside method **new Camera.Area(focusRect, 1000)** mean.My rectangle is an area which i use to capture camera @MartynasJurkus – shadow Dec 18 '19 at 02:16
@shadow represents area weight. It is used when calculating metering and focus areas. Possible values from 0 to 1000. The bigger the value the bigger influence the area has for the final result – Martynas Jurkus Dec 19 '19 at 12:37
@MartynasJurkus so If i have 1 rectangle center of the camera.I use "setFocusArea" with parameter is that rectangle and weight is 1.So it will only focus on my rectangle right? – shadow Dec 20 '19 at 03:55

ivan.panasiuk · Answer 2 · 2016-03-30T12:07:13.817

5

Beside setting:

parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);

you need to set:

parameters.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

if you want real 'live' auto-focus. Also, it will be good to check available focuses:

List<String> focusModes = parameters.getSupportedFocusModes();
LLog.d("focusModes=" + focusModes);
if (focusModes.contains(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE))
    parameters.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

On Samsung S6 you must set this with little delay (~ 500 ms) after getting camera preview.

edited Mar 30 '16 at 12:07

answered Mar 27 '16 at 14:24

ivan.panasiuk

1,239
16
20

Whats the best way to switch between Auto and continuous? Let's say user taps and we use auto focus and he moves the frame we re set it to continuous? – Cyph3rCod3r Nov 02 '18 at 06:03

score 3 · Answer 3 · answered Sep 29 '13 at 00:28

3

I had this problem today :/

And after hours of struggling, I found the solution!

It's strange, but it appears that setting focus-mode to "macro" right before setting focus-areas solved the problem ;)

params.setFocusMode(Camera.Parameters.FOCUS_MODE_MACRO);
params.setFocusAreas(focusAreas);
mCamera.setParameters(params);

I have Galaxy S3 with Android 4.1.2

I hope this will work for you either :)

answered Sep 29 '13 at 00:28

Grzegorz D.

1,748
15
18

Yeah on s3, s4 with 4.3 & 5.0.1 it works well but not working on htc one – Ahmad Arslan Jun 01 '15 at 07:20

score 2 · Answer 4 · answered Jan 12 '17 at 15:26

use FOCUS_MODE_FIXED

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
        mCamera = Camera.open(mCameraId);
    } else {
        mCamera = Camera.open();
    }
cameraParams = mCamera.getParameters();
// set the focus mode
cameraParams.setFocusMode(Camera.Parameters.FOCUS_MODE_FIXED);
// set Camera parameters
mCamera.setParameters(cameraParams);

amiron · Answer 5 · 2019-10-09T17:53:18.337

Hi, try below code copy and change for yourself

public class CameraActivity extends AppCompatActivity implements Camera.AutoFocusCallback {

    private Camera camera;
    private FrameLayout fl_camera_preview;

    ...

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView( R.layout.camera_activity );
        //this View, is lens camera 
        fl_camera_preview = findViewById( R.id.fl_camera_preview );
        Button someButtonCapturePicture = findViewById(R.id.someButtonCapturePicture);

        pictureCall = getPictureCallback();

        //check camera access
        if ( getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA) ) {

            if ( safeCameraOpen(0) ) {

                cameraPreview = new CameraPreview( this, camera );
                fl_camera_preview.addView( cameraPreview );

                someButtonCapturePicture.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {

                        camera.takePicture(null, null, pictureCall);

                    }
                });

            } else {
                Log.w(TAG, "getCameraInstance:  Camera is not available (in use or does not exist)." );
            }        

        }

    }

    private boolean safeCameraOpen(int id) {

        boolean qOpened = false;

        try {

            camera = Camera.open( id );
            // set some parameters
            Camera.Parameters par = camera.getParameters();

        List<Camera.Size> supportedPreviewSizes = par.getSupportedPreviewSizes();

            for ( Camera.Size cs : supportedPreviewSizes ) {
              if ( cs.height == 720 ) {
                 par.setPictureSize(cs.width, cs.height);
                 par.setPreviewSize(cs.width, cs.height);
                 break;
              }
            }

            camera.setParameters(par);

            qOpened = ( camera != null );

        } catch (Exception e) {
            Log.e(TAG, "safeCameraOpen: failed to open Camera");
            e.printStackTrace();
        }

        return qOpened;

    }

    public void touchFocusCamera( final Rect touchFocusRect ) {

        //Convert touche coordinate, in width and height to -/+ 1000 range
        final Rect targetFocusRect = new Rect(
                touchFocusRect.left * 2000/fl_camera_preview.getWidth() - 1000,
                touchFocusRect.top * 2000/fl_camera_preview.getHeight() - 1000,
                touchFocusRect.right * 2000/fl_camera_preview.getWidth() - 1000,
                touchFocusRect.bottom * 2000/fl_camera_preview.getHeight() - 1000);

        final List<Camera.Area> focusList = new ArrayList<Camera.Area>();
        Camera.Area focusArea = new Camera.Area(targetFocusRect, 1000);
        focusList.add(focusArea);

        Camera.Parameters para = camera.getParameters();
        List<String> supportedFocusModes = para.getSupportedFocusModes();
        if ( supportedFocusModes != null &&
                supportedFocusModes.contains(Camera.Parameters.FOCUS_MODE_AUTO) ) {

            try {

                para.setFocusAreas(focusList);
                para.setMeteringAreas(focusList);
                camera.setParameters(para);

                camera.autoFocus( CameraActivity.this );

            } catch (Exception e) {
                Log.e(TAG, "handleFocus: " + e.getMessage() );
            }

        }

    }

    @Override
    public void onAutoFocus(boolean success, Camera camera) {

        if ( success ) {
            camera.cancelAutoFocus();
        }

        float focusDistances[] = new float[3];
        camera.getParameters().getFocusDistances(focusDistances);

    }

    /**
     * Get Bitmap from camera
     * @return picture
     */
    private Camera.PictureCallback getPictureCallback() {

        Camera.PictureCallback picture = new Camera.PictureCallback() {
            @Override
            public void onPictureTaken(byte[] data, Camera camera) {

                Log.i(TAG, "onPictureTaken: size bytes photo: " + data.length );

            }
        };

        return picture;

    }

    ...

}

//And SurfaceView with Callback
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

    private static final String TAG = "CameraPreview";
    SurfaceHolder holder;
    Camera camera;

    public CameraPreview( Context context, Camera _camera ) {
        super(context);

        camera = _camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        holder = getHolder();
        holder.addCallback(this);

        // deprecated setting, but required on Android versions prior to 3.0
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        // The Surface has been created, now tell the camera where to draw the preview.
        try {

            camera.setPreviewDisplay(holder);
            camera.startPreview();

        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        if( event.getAction() == MotionEvent.ACTION_DOWN ) {

            // Get the pointer's current position
            float x = event.getX();
            float y = event.getY();
            float touchMajor = event.getTouchMajor();
            float touchMinor = event.getTouchMinor();

            Rect touchRect = new Rect(
                    (int)(x - touchMajor/2),
                    (int)(y - touchMinor/2),
                    (int)(x + touchMajor/2),
                    (int)(y + touchMinor/2));

            ((CameraActivity)getContext())
                        .touchFocusCamera( touchRect );

        }

        return true;

    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (this.holder.getSurface() == null) {
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            camera.stopPreview();
        } catch (Exception e) {
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            camera.setPreviewDisplay(this.holder);
            camera.startPreview();

        } catch (Exception e) {
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }

    }

    ...

}

Android setFocusArea and Auto Focus

5 Answers5

Update

Linked