android camera2 处理每一帧并显示其预览

Question

我使用 https://github.com/googlesamples/android-Camera2Basic ，但尝试以一种我可以在将每一帧绘制到 surfaceview 之前访问它的方式对其进行修改。我明白了，我应该添加额外的表面 (ImageReader.getSurface())，并在此回调中从中读取帧:

private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
            = new ImageReader.OnImageAvailableListener() {

        @Override
        public void onImageAvailable(ImageReader reader) {

           Log.d("Img", "onImageAvailable");
            mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));
        }

    };

问题是只有当图像被用户捕获时才会调用此回调，而不是在从相机发送到预览屏幕的每个帧上。

这是我尝试添加的内容:

private void createCameraPreviewSession() {
        try {
            SurfaceTexture texture = mTextureView.getSurfaceTexture();
            assert texture != null;

            // We configure the size of default buffer to be the size of camera preview we want.
            texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());

            // This is the output Surface we need to start preview.
            Surface surface = new Surface(texture);

            // We set up a CaptureRequest.Builder with the output Surface.
            mPreviewRequestBuilder
                    = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            mPreviewRequestBuilder.addTarget(surface);

            // Here, we create a CameraCaptureSession for camera preview.
            mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
                    new CameraCaptureSession.StateCallback() {

                        @Override
                        public void onConfigured(CameraCaptureSession cameraCaptureSession) {
                            // The camera is already closed
                            if (null == mCameraDevice) {
                                return;
                            }

                            // When the session is ready, we start displaying the preview.
                            mCaptureSession = cameraCaptureSession;
                            try {
                                // Auto focus should be continuous for camera preview.
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                                // Flash is automatically enabled when necessary.
                                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                                        CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

                                // Finally, we start displaying the camera preview.
                                mPreviewRequest = mPreviewRequestBuilder.build();
                                mCaptureSession.setRepeatingRequest(mPreviewRequest,
                                        mCaptureCallback, mBackgroundHandler);
                                //mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                            showToast("Failed");
                        }
                    }, null
            );

            /**TODO added for capturing aeach frame*/
            // This is the CaptureRequest.Builder that we use to take a picture.
            final CaptureRequest.Builder captureBuilder =
                    mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            captureBuilder.addTarget(mImageReader.getSurface());

            // Use the same AE and AF modes as the preview.
            captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            captureBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                    CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);

            /**end added for capture each frame*/


        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

Answer 1

无需创建 CaptureRequest.Builder 的新实例，只需将 ImageReader 的 Surface 添加到 mPreviewRequestBuilder 的输出目标。