使用opencv android，如何在打开相机时自动剪切视频帧答案

【问题标题】：Using opencv4android,how to cut out video frame automatically when the camera is opened使用opencv android，如何在打开相机时自动剪切视频帧
【发布时间】：2017-06-09 10:56:37
【问题描述】：

官方SDK中有一个可以截取视频帧的示例。主要代码如下：

@SuppressLint("SimpleDateFormat")
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        Log.i(TAG,"onTouch event");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss");
        String currentDateandTime = sdf.format(new Date());
        String fileName = Environment.getExternalStorageDirectory().getPath() +
                               "/sample_picture_" + currentDateandTime + ".jpg";
        mOpenCvCameraView.takePicture(fileName);
        Toast.makeText(this, fileName + " saved", Toast.LENGTH_SHORT).show();
        return false;
    }

现在我想把它改成一个可以自动剪掉视频帧的样本。我已经评论了上面的代码并更改了名为 onManagerConnected.变化如下：

private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS:
                {
                    Log.i(TAG, "OpenCV loaded successfully");
                    mOpenCvCameraView.enableView();
                    String filename = Environment.getExternalStorageDirectory().getPath()+"test"+".jpg";
                    mOpenCvCameraView.takePicture(filename);
                    Log.i(TAG, filename);
//                  mOpenCvCameraView.setOnTouchListener(Tutorial3Activity.this);
                } break;
                default:
                {
                    super.onManagerConnected(status);
                } break;
            }
        }
    };

然后抛出一个 nullpointException，显示 var "mPictureFileName" 和 "mCamera" 为 null。

 public void takePicture(final String fileName) {
            Log.i(TAG, "Taking picture");
            mPictureFileName = fileName;
            // Postview and jpeg are sent in the same buffers if the queue is not empty when performing a capture.
            // Clear up buffers to avoid mCamera.takePicture to be stuck because of a memory issue
            mCamera.setPreviewCallback(null);

            // PictureCallback is implemented by the current class
            mCamera.takePicture(null, null, this);
        }

不管怎样！

感谢您的回答！

【问题讨论】：

标签： opencv4android

【解决方案1】：

当视图打开时，相机没有启动。因此您不能在“启动”方法中剪切视频。我将这些代码移至方法“onCameraFrame”。完成！

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    String filename = null;
    filename = Environment.getExternalStorageDirectory().getPath()+"/test"+i+".jpg";
    mOpenCvCameraView.takePicture(filename);
    Log.d("camera", filename);
    return inputFrame.rgba();
}

【讨论】：