Rotate camera preview to Portrait Android OpenCV Camera

Question

I am trying to use OpenCV 2.4.3.2 to create a camera app and do some opencv processing. I would like it to be able to have multiple UI orientations, not just Landscape.

Answer 1

Thanks to @Kaye Wrobleski for his answer. I have extended it to allow both landscape and portrait orientation. This is basically just a little extra code to allow easily switching between the default code that gives landscape orientation, and his code for portrait.

Insert his code as a new method in CameraBridgeViewBase.java

protected void deliverAndDrawFramePortrait(CvCameraViewFrame frame) {
        Mat modified;

        if (mListener != null) {
            modified = mListener.onCameraFrame(frame);
        } else {
            modified = frame.rgba();
        }

        boolean bmpValid = true;
        if (modified != null) {
            try {
                Utils.matToBitmap(modified, mCacheBitmap);
            } catch(Exception e) {
                Log.e(TAG, "Mat type: " + modified);
                Log.e(TAG, "Bitmap type: " + mCacheBitmap.getWidth() + "*" + mCacheBitmap.getHeight());
                Log.e(TAG, "Utils.matToBitmap() throws an exception: " + e.getMessage());
                bmpValid = false;
            }
        }

        if (bmpValid && mCacheBitmap != null) {
            Canvas canvas = getHolder().lockCanvas();
            // Rotate canvas to 90 degrees
            canvas.rotate(90f, canvas.getWidth()/2, canvas.getHeight()/2);
            if (canvas != null) {
                canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
                Log.d(TAG, "mStretch value: " + mScale);

                if (mScale != 0) {
                    // Resize
                    Bitmap bitmap = Bitmap.createScaledBitmap(mCacheBitmap, canvas.getHeight(), canvas.getWidth(), true);
                    // Use bitmap instead of mCacheBitmap
                    canvas.drawBitmap(bitmap, new Rect(0,0,bitmap.getWidth(), bitmap.getHeight()), new Rect(
                            (int)((canvas.getWidth() - mScale*bitmap.getWidth()) / 2),
                            (int)((canvas.getHeight() - mScale*bitmap.getHeight()) / 2),
                            (int)((canvas.getWidth() - mScale*bitmap.getWidth()) / 2 + mScale*bitmap.getWidth()),
                            (int)((canvas.getHeight() - mScale*bitmap.getHeight()) / 2 + mScale*bitmap.getHeight())), null);
                } else {
                    Bitmap bitmap = Bitmap.createScaledBitmap(mCacheBitmap, canvas.getHeight(), canvas.getWidth(), true);
                    // Use bitmap instead of mCacheBitmap
                    canvas.drawBitmap(bitmap, new Rect(0,0,bitmap.getWidth(), bitmap.getHeight()), new Rect(
                            (int)((canvas.getWidth() - bitmap.getWidth()) / 2),
                            (int)((canvas.getHeight() - bitmap.getHeight()) / 2),
                            (int)((canvas.getWidth() - bitmap.getWidth()) / 2 + bitmap.getWidth()),
                            (int)((canvas.getHeight() - bitmap.getHeight()) / 2 + bitmap.getHeight())), null);
                }

                if (mFpsMeter != null) {
                    mFpsMeter.measure();
                    mFpsMeter.draw(canvas, 20, 30);
                }
                getHolder().unlockCanvasAndPost(canvas);
            }
        }
    }

Then modify JavaCameraView.java

Add a new variable to track whether we are in portrait or landscape mode

private boolean portraitMode;

Add two methods to set the orientation mode

public void setLandscapeMode() {
        portraitMode = false;
    }
    public void setPortraitMode() {
        portraitMode = true;
    }

Now replace these lines in the JavaCameraView CameraWorkerClass, run() method

if (!mFrameChain[1 - mChainIdx].empty())
                        deliverAndDrawFrame(mCameraFrame[1 - mChainIdx]);

With these lines:

if (!mFrameChain[1 - mChainIdx].empty()) {
                        if (!portraitMode) {
                            deliverAndDrawFrame(mCameraFrame[1 - mChainIdx]);
                        } else {
                            deliverAndDrawFramePortrait(mCameraFrame[1 - mChainIdx]);
                        }
                    }

To switch between orientations, simply call either setLandscapeMode() or setPortraitMode() on your JavaCameraView object.

Please note that reverse portrait and reverse landscape orientations will still be upside-down. You will need to rotate them 180 degrees to get them right-side up, which is easily done with OpenCV's warpAffine() method. Note when using the back camera (LENS_FACING_BACK), portrait mode will flip the images upside down.