/*
     * Camera management
     */

    /**
     * Selects the last used camera or a front-facing one
     */
    public void selectCamera()
    {
        int cameraID = preferences.getInt("cameraID", -1);
        if (cameraID == -1)
        {
            // no camera was selected previously, select a front-facing one
            int nCameras = Camera.getNumberOfCameras();

            CameraInfo cameraInfo = new CameraInfo();
            for (int i = 0; i < nCameras; i++)
            {
                Camera.getCameraInfo(i, cameraInfo);
                if (cameraInfo.facing == CameraInfo.CAMERA_FACING_FRONT)
                {
                    cameraID = i;
                }
            }

            // there's no front camera
            if (cameraID == -1)
            {
                cameraID = 0;
            }
        }

        setPreviewSurface(previewSurface);
        setupCamera(cameraID);
    }

    /**
     * Sets the camera used for face detection
     *
     * @param cameraID the ID of the camera to use
     */
    public void setupCamera(int cameraID)
    {
        // release previous one
        if (camera != null)
        {
            camera.release();
            camera = null;
        }

        // save selection
        Editor editor = preferences.edit();
        editor.putInt("cameraID", cameraID);
        editor.commit();

        try
        {
            // open camera
            camera = Camera.open(cameraID);

            // get smallest available preview size
            Parameters params = camera.getParameters();
            List<Size> psizes = params.getSupportedPreviewSizes();
            Collections.sort(psizes, new Comparator<Size>()
            {
                @Override
                public int compare(Size size1, Size size2)
                {
                    long pixels1 = size1.height * size1.width;
                    long pixels2 = size2.height * size2.width;

                    return (pixels1 < pixels2) ? -1 : (pixels1 > pixels2) ? 1 : 0;
                }
            });
            Size smallest = psizes.get(0);
            params.setPreviewSize(smallest.width, smallest.height);

            // set preferred preview format
            params.setPreviewFormat(ImageFormat.NV21);

            // save parameters
            camera.setParameters(params);

            // set preview display
            camera.setPreviewDisplay(previewSurface.getHolder());

            // set orientation
            CameraInfo info = new CameraInfo();
            Camera.getCameraInfo(cameraID, info);
            WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
            int _rotation = wm.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 = (360 + info.orientation - degrees) % 360;
            rotation = degrees;

            camera.setDisplayOrientation(result);
            swapMetrics = (result % 180 == 0);

            // set camera in imageprocessor
            if (processor != null)
                processor.setCamera(camera, result);

            calculator.loadSettings();

            // start preview
            camera.startPreview();
        }
        catch (Exception e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }