Zoom Camera2 Preview using TextureView

Question

i have a Problem with my Preview Zoom for the Camera2 API. I am using a TextureView.

I want to zoom only the preview Stream that was showed in the TextureView.

Answer 1

Here is a Pan and Zoom object from Camera2 that I made to work using the OnScaleGestureListener and SimpleOnGestureListener-onScroll outputs. This will only work as expected if you have a camera with support level > LEGACY, as LEGACY only supports crop to center.

Two caveats: One is that this is currently NOT set up to output to JPEG output, as rectangles for JPEG outputs must have dimensions which are multiple of 16 (See why here). The second is that I've locked my screen to landscape mode, and my camera is locked to landscape as well, but it should be possible to deal with screen rotations after a few tweaks.

You'll need to pass in the screen dimensions

DisplayMetrics displayMetrics = new DisplayMetrics();
((Activity) mView.getContext()).getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);

the Maximum Camera Digital Zoom

try {
    CameraManager manager = (CameraManager) mView.getContext().getSystemService(Context.CAMERA_SERVICE);
    CameraCharacteristics characteristics = manager.getCameraCharacteristics(mCameraID);
    float maxZoom = (characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM));
} catch (CameraAccessException e) {
   e.printStackTrace();
}

the Camera Sensor's Active Array Size

try {
    CameraManager manager = (CameraManager) mView.getContext().getSystemService(Context.CAMERA_SERVICE);
    CameraCharacteristics characteristics = manager.getCameraCharacteristics(mCameraID);
    Rect rectInit = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
} catch (CameraAccessException e) {
    e.printStackTrace();
}

Here is my object initialization

mScaler = new CamScaler(maxZoom, rectInit.width(), rectInit.height(), displayMetrics.heightPixels, displayMetrics.widthPixels);

the CamScaler class

public class CamScaler {
    private final float ZOOM_MIN = 1.0f;
    private final int X_MIN = 0;
    private final int Y_MIN = 0;
    private int displayWidth;
    private int displayHeight;

    private Rect current_rect;
    private int xCenter;
    private int yCenter;
    private int xWidth;
    private int yHeight;
    private int xMax;
    private int yMax;
    private float zoomMax;
    private float zoomCurrent;

    public CamScaler(float zoomMax, int xMax, int yMax, int displayHeight, int displayWidth) {
        this.xMax = xMax;
        this.yMax = yMax;
        this.zoomMax = zoomMax;

        current_rect = new Rect(X_MIN,Y_MIN, xMax, yMax); //(0,0,xMax,yMax) as the starting rectangle
        zoomCurrent = ZOOM_MIN;
        xWidth = current_rect.width();
        yHeight = current_rect.height();
        xCenter = current_rect.centerX();
        yCenter = current_rect.centerY();

        this.displayHeight = displayHeight;
        this.displayWidth = displayWidth;
    }

    public void pan(float distanceX, float distanceY){
        //calculate the shift in the we want to take on the camera sensor with respect to the distance moved on the screen
        int xShift = Math.round((distanceX/displayWidth)*xWidth); //scales down to a percentage of the current view width->converts to a pixel shift
        int yShift = Math.round((distanceY/displayHeight)*yHeight); //scales down to a percentage of the current view height->converts to a pixel shift

        //check if the shift will push us pass our maximums, this should account for both negative and positive values of xShift and yShift correctly
        if ( !((xCenter + Math.round(xWidth/2.0) + xShift < xMax) && (xCenter - Math.round(xWidth/2.0) + xShift > 0))) { //if not within xBounds, set xShift to 0
            xShift = 0;
        }
        if ( !((yCenter + Math.round(yHeight/2) + yShift < yMax) && (yCenter - Math.round(yHeight/2.0) + yShift > 0))) { //if not within yBounds, set yShift to 0
            yShift = 0;
        }

        Log.d("Scaler", "pan: xShift" + xShift + " yShift " + yShift);
        current_rect.offset(xShift,yShift);
        Log.d("Scaler", "pan: current_rect" + current_rect.toString());
        xCenter = current_rect.centerX(); //update center
        yCenter = current_rect.centerY(); //update center
    }

    public void zoom(float scale_change){
        if ( (zoomCurrent*scale_change < zoomMax) && (zoomCurrent*scale_change > ZOOM_MIN) ){ //if we are within zoom bounds
            zoomCurrent *= scale_change; //update the zoom factor
            int newWidthHalf = (int)Math.floor(xMax/zoomCurrent/2.0);
            int newHeightHalf = (int)Math.floor(yMax/zoomCurrent/2.0);
            int xTempCenter = xCenter;
            int yTempCenter = yCenter;

            //if at edge we need to shift and scale
            if (xCenter + newWidthHalf > xMax) { //if at right edge
                xTempCenter = xMax - newWidthHalf; //shift center to the left
            } else if (xCenter - newWidthHalf < 0) { //if at left edge
                xTempCenter = newWidthHalf; //shift center to the right
            }
            if (yCenter + newHeightHalf > yMax) { //if at bottom
                yTempCenter = yMax - newHeightHalf; //shift center up
            } else if (yCenter - newHeightHalf < 0) { //if at top
                yTempCenter = newHeightHalf; //shift center down
            }
            Log.d("Scaler", "zoom: " + zoomCurrent);
            Log.d(TAG, "current center(x,y) " + xTempCenter + " " + yTempCenter + "current halfwidths(x,y) " + newWidthHalf + " " + newHeightHalf);
            current_rect.set(xTempCenter - newWidthHalf, yTempCenter - newHeightHalf,xTempCenter + newWidthHalf, yTempCenter + newHeightHalf);
            Log.d("Scaler", "zoom: current_rect" + current_rect.toString());
            xWidth = current_rect.width();
            yHeight = current_rect.height();
            xCenter = current_rect.centerX(); //update center
            yCenter = current_rect.centerY(); //update center
        } //if not in digital zoom bounds, do nothing
    }

    public Rect getCurrentView() {
        return current_rect;
    }
}

And how to use it

public void pan(float distanceX, float distanceY){
    if (mScaler != null) {
        synchronized (mScaler) {
            mScaler.pan(distanceX, distanceY);
            try {
                mPreviewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, mScaler.getCurrentView());
                mCaptureSession.setRepeatingRequest(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
    }
}

public void zoom(float scale_factor) {
    if (mScaler!= null) {
        synchronized (mScaler) {
            mScaler.zoom(scale_factor);
            try {
                mPreviewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, mScaler.getCurrentView());
                mCaptureSession.setRepeatingRequest(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
    }
}

The inputs to these functions are directly passed through from the gesture listeners

I hope this helps someone!