android - 如何使用 camera2 API 修复 Nexus 5x 上的 "reverse landscape"问题

Question

我的应用使用 camera2 API 管理来自设备相机的预览。但问题是我的设备是 Nexus 5x，具有翻转传感器和众所周知的反向景观“问题”。我在某处读到 camera2 api 会“自动”处理此问题，但我认为只有当您在设置捕获 session 时以 Surface View 对象的表面为目标时，这才是正确的。但是我的目标是建立在表面纹理之上的表面，我进一步使用它来渲染预览以获得立体 View ，并且通过这种方法问题仍然存在，我得到了颠倒的帧。这是代码，几乎是使用 camera2 API 时的常规工作流程。

private void openCamera() {
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    Log.e(TAG, "is camera open");
    try {
        cameraId = manager.getCameraIdList()[CAMERA_SOURCE];
        CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
        StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
        assert map != null;
        imageDimension = map.getOutputSizes(SurfaceTexture.class)[CAMERA_SOURCE];
        // Add permission for camera and let user grant the permission
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CAMERA_PERMISSION);
            return;
        }
        manager.openCamera(cameraId, stateCallback, null);

    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
    Log.e(TAG, "openCamera X");
}

private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        //This is called when the camera is open
        Log.e(TAG, "onOpened");
        cameraDevice = camera;
        createCameraPreview();
    }
    @Override
    public void onDisconnected(CameraDevice camera) {
        cameraDevice.close();
    }
    @Override
    public void onError(CameraDevice camera, int error) {
        cameraDevice.close();
        cameraDevice = null;
    }
};

protected void createCameraPreview() {
    try {

        // Create ImageReader Surface
        int max = 2;
        mReader = ImageReader.newInstance(mWidth, mHeight, ImageFormat.YUV_420_888, max);
        ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
            @Override
            public void onImageAvailable(ImageReader mReader) {
                Image image = null;
                image = mReader.acquireLatestImage();
                if (image == null) {
                    return;
                }                           

                byte[] bytes = convertYUV420ToNV21(image);

                nativeVideoFrame(bytes);
                image.close();   
            }
        };      

        mReader.setOnImageAvailableListener(readerListener, mBackgroundHandler);

        // Create Texture Surface
        texture = createTexture();
        mSurfaceTexture = new SurfaceTexture(texture);
        mSurfaceTexture.setOnFrameAvailableListener(this);
        mSurfaceTexture.setDefaultBufferSize(imageDimension.getWidth(), imageDimension.getHeight());
        mSurface = new Surface(mSurfaceTexture);

        //Attach surfaces to CaptureRequest
        List<Surface> outputSurfaces = new ArrayList<Surface>(2);
        outputSurfaces.add(mReader.getSurface());
        outputSurfaces.add(mSurface);
        captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        captureRequestBuilder.addTarget(mSurface);
        captureRequestBuilder.addTarget(mReader.getSurface());

        //Define the capture request
        cameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback(){
                    @Override
                    public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                        //The camera is already closed
                        if (null == cameraDevice) {
                            return;
                        }
                        // When the session is ready, we start displaying the preview.
                        cameraCaptureSessions = cameraCaptureSession;
                        updatePreview();
                    }
                    @Override
                    public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                        Toast.makeText(MainActivity.this, "Configuration change", Toast.LENGTH_SHORT).show();
                    }
                }, null);
        } catch (CameraAccessException e) {
             e.printStackTrace();
        }
}

protected void updatePreview() {
    if(null == cameraDevice) {
        Log.e(TAG, "updatePreview error, return");
    }
    captureRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
    try {
        cameraCaptureSessions.setRepeatingRequest(captureRequestBuilder.build(), null, mBackgroundHandler);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

我的问题是:我应该怎么做才能自己解决反向横向问题？我应该在哪一行代码和哪里添加？

谢谢，

JM

Answer 1

由于您使用的是 SurfaceTexture 和 ImageReader，因此您必须自己处理旋转。当与 SurfaceView 或 TextureView 结合使用时，Camera2 API 会自动处理旋转。

也就是说，您可以在通过 ImageReader.OnImageAvailableListener 回调获取帧字节后手动旋转它们，或者甚至更好地直接在 GPU 上对 OpenGL 纹理执行操作。

请注意，旋转 180° 相当于垂直翻转一次和水平翻转一次字节，这在 OpenGL 上意味着可以:

• 将绘制相机纹理的平面旋转 180°
• 将绘制相机纹理的平面的 x 和 y 缩放 -1
• 更改相机平面的 UV