Android jpeg pictureCallback到灰度Opencv Mat

Question

首先，我尝试使用rawPicture回调，但总是得到空指针。

 mCamera.takePicture(null, mPicture, null);

JpegCalback给出了not null byte[]数组，但是cvtColor转换不起作用。

mCamera.takePicture(null, null, mPicture);

我的预览回调如下

Camera.PictureCallback mPicture = new Camera.PictureCallback() {
    @Override
        public void onPictureTaken(byte[] data, Camera camera) {

        Toast.makeText(getApplicationContext(),"picture taken",Toast.LENGTH_SHORT);
        int res=JniManager.setImage(data,m_width,m_height);
        mCamera.stopPreview();
        mCamera.startPreview();
    }
};

C++JNI函数：

    Java_pidaas_vicomtech_org_facerec_viulib_JniManager_setImage(JNIEnv *env,
                                                    jobject instance,
                                                    jbyteArray image,
                                                    jint width,
                                                    jint height)
     jbyte* _yuv  = env->GetByteArrayElements(image, 0);
     int len = env->GetArrayLength (image);
     unsigned char* buf = new unsigned char[len];
     env->GetByteArrayRegion (image, 0, len, reinterpret_cast<jbyte*>(buf));
     Mat rawData (cv::Size(width,height), CV_8UC3, buf );
            cv::Mat test =imdecode(rawData,CV_LOAD_IMAGE_COLOR);
            cv::Mat grey;
            cv::cvtColor(test, grey, cv::COLOR_BGR2GRAY);
            bool flag = imwrite("/sdcard/graypg.jpg", grey);
    env->ReleaseByteArrayElements(image, _yuv, 0);
}

我找到了一些答案，但都不起作用。

• 带有raw PicturecallBack的Android相机的格式是什么？
• 如何在OpenCV中将CV：：Mat转换为灰度？
• OpenCV从缓冲区读取jpeg图像