Take photos using the Camera2 API

However, I successfully resolved the black color issue as follows :

First, in case anyone is wondering, you actually DO NOT need any kind of activity or any kind of preview preview element like so many other topics about camera API approval! This was true for the deprecated Camera API v1. Now, with the new Camera v2 API, all I needed was the foreground.

To start the capture process, I used this code:

CaptureRequest.Builder builder = cameraDevice.createCaptureRequest (CameraDevice.TEMPLATE_VIDEO_SNAPSHOT);
builder.set (CaptureRequest.CONTROL_MODE, CaptureRequest.CONTROL_MODE_AUTO);
builder.set (CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF);
builder.addTarget (imageReader.getSurface ());
captureRequest = builder.build ();

      

        
        
        
      

    

Then, in ImageReader.onImageAvailable, I skipped the first N pictures (which means I didn't save them). I let the session run and capture more photos without saving them.

This gave the camera enough time to automatically adjust the exposure settings. Then, after N photos being ignored, I saved the photo, which was usually exposed, not black.

The value of the constant N will depend on the characteristics of your equipment. Thus, you will need to determine the ideal N value experimentally for your equipment. You can also use histogram-based heuristic automation. When you start experimenting, don't be afraid to start saving only after hundreds of milliseconds of calibration have passed.

Finally, in many similar streams, people suggest just waiting, for example. 500ms after creating a session and only then using one snapshot. It does not help. ... What you really need to do is let the camera work and let you take many photos quickly (at maximum speed). To do this, just use the setRepeatingRequest method (as in your original code).

Hope this helps. :)

SHOULD BE ADDED: When skipping the original N images, you need to call the LastImage ImageReader getter for each of the skipped images. Otherwise it won't work.

Full source code with included changes that resolved the issue, tested and verified to work on Google Pixel 2, Android 8.1 :

public class Camera2Service extends Service
{
    protected static final int CAMERA_CALIBRATION_DELAY = 500;
    protected static final String TAG = "myLog";
    protected static final int CAMERACHOICE = CameraCharacteristics.LENS_FACING_BACK;
    protected static long cameraCaptureStartTime;
    protected CameraDevice cameraDevice;
    protected CameraCaptureSession session;
    protected ImageReader imageReader;

    protected CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(@NonNull CameraDevice camera) {
            Log.d(TAG, "CameraDevice.StateCallback onOpened");
            cameraDevice = camera;
            actOnReadyCameraDevice();
        }

        @Override
        public void onDisconnected(@NonNull CameraDevice camera) {
            Log.w(TAG, "CameraDevice.StateCallback onDisconnected");
        }

        @Override
        public void onError(@NonNull CameraDevice camera, int error) {
            Log.e(TAG, "CameraDevice.StateCallback onError " + error);
        }
    };

    protected CameraCaptureSession.StateCallback sessionStateCallback = new CameraCaptureSession.StateCallback() {

        @Override
        public void onReady(CameraCaptureSession session) {
            Camera2Service.this.session = session;
            try {
                session.setRepeatingRequest(createCaptureRequest(), null, null);
                cameraCaptureStartTime = System.currentTimeMillis ();
            } catch (CameraAccessException e) {
                Log.e(TAG, e.getMessage());
            }
        }


        @Override
        public void onConfigured(CameraCaptureSession session) {

        }

        @Override
        public void onConfigureFailed(@NonNull CameraCaptureSession session) {
        }
    };

    protected ImageReader.OnImageAvailableListener onImageAvailableListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Log.d(TAG, "onImageAvailable");
            Image img = reader.acquireLatestImage();
            if (img != null) {
                if (System.currentTimeMillis () > cameraCaptureStartTime + CAMERA_CALIBRATION_DELAY) {
                    processImage(img);
                }
                img.close();
            }
        }
    };

    public void readyCamera() {
        CameraManager manager = (CameraManager) getSystemService(CAMERA_SERVICE);
        try {
            String pickedCamera = getCamera(manager);
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                return;
            }
            manager.openCamera(pickedCamera, cameraStateCallback, null);
            imageReader = ImageReader.newInstance(1920, 1088, ImageFormat.JPEG, 2 /* images buffered */);
            imageReader.setOnImageAvailableListener(onImageAvailableListener, null);
            Log.d(TAG, "imageReader created");
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
    }

    public String getCamera(CameraManager manager){
        try {
            for (String cameraId : manager.getCameraIdList()) {
                CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
                int cOrientation = characteristics.get(CameraCharacteristics.LENS_FACING);
                if (cOrientation == CAMERACHOICE) {
                    return cameraId;
                }
            }
        } catch (CameraAccessException e){
            e.printStackTrace();
        }
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand flags " + flags + " startId " + startId);

        readyCamera();

        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onCreate() {
        Log.d(TAG,"onCreate service");
        super.onCreate();
    }

    public void actOnReadyCameraDevice()
    {
        try {
            cameraDevice.createCaptureSession(Arrays.asList(imageReader.getSurface()), sessionStateCallback, null);
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
    }

    @Override
    public void onDestroy() {
        try {
            session.abortCaptures();
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
        session.close();
    }


     private void processImage(Image image){
    //Process image data
    ByteBuffer buffer;
    byte[] bytes;
    boolean success = false;
    File file = new File(Environment.getExternalStorageDirectory() + "/Pictures/image.jpg");
    FileOutputStream output = null;

    if(image.getFormat() == ImageFormat.JPEG) {
        buffer = image.getPlanes()[0].getBuffer();
        bytes = new byte[buffer.remaining()]; // makes byte array large enough to hold image
        buffer.get(bytes); // copies image from buffer to byte array
        try {
            output = new FileOutputStream(file);
            output.write(bytes);    // write the byte array to file
            j++;
            success = true;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            image.close(); // close this to free up buffer for other images
            if (null != output) {
                try {
                    output.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }


}

protected CaptureRequest createCaptureRequest() {
    try {
        CaptureRequest.Builder builder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
        builder.addTarget(imageReader.getSurface());
        return builder.build();
    } catch (CameraAccessException e) {
        Log.e(TAG, e.getMessage());
        return null;
    }
}

@Override
public IBinder onBind(Intent intent) {
    return null;
}

      

        
        
        
      

    

}