OpenCV (C++): how to save a 16bit image?

Question

I'm working with kinect, and I need to save RAW depth image. This means that I shouldn't save it with a conversion to 8 bit (that is what imwrite is doing!) but save it as 16 bit, without have any bit-depth reducing. I hope that this question will not be too trivial, but I'm new to OpenCV programming. I tried the following, but it doesn't work:

[...]

Mat imageDepth ( 480, 640, CV_16UC1 );
Mat imageRGB;

// Video stream settings
VideoCapture capture;
capture.open( CAP_OPENNI );

if ( !capture.isOpened() ) {
  cerr << "Cannot get video stream!" << endl;
  exit ( EXIT_WITH_ERROR );
}

if ( !capture.grab() ) {
  cerr << "Cannot grab images!" << endl;
  exit ( EXIT_WITH_ERROR );
}

// Getting frames
if ( capture.retrieve( imageDepth, CAP_OPENNI_DISPARITY_MAP ) ) {
  imwrite( fileDepth, imageDepth );
}
if( capture.retrieve( imageRGB, CAP_OPENNI_BGR_IMAGE ) ) {
  imwrite( fileRGB, imageRGB );
}

return EXIT_WITH_SUCCESS;

Thanks in advance.

Answer 1

The problem wasn't in the way the image was saved, that was all right (if someone will have the same problem, be sure to save in PNG/TIFF format and specify CV_16UC1 when reading). It wasn't saved as 16bit because of VideoCapture; in fact I did the following:

if ( capture.retrieve( imageDepth, CAP_OPENNI_DISPARITY_MAP ) ) {
   imwrite( fileDepth, imageDepth );
}

But the correct way to do it is:

if ( capture.retrieve( imageDepth, CAP_OPENNI_DEPTH_MAP ) ) {
  imwrite( fileDepth, imageDepth );
}

So it was a silly problem.
Thanks to all the people who tried to help me.

Answer 2

My imwrite in opencv does not seem to support 16-bit image storage. So, I used the OpenCV FileStorage Class.

Next is the relevant code snippet. WRITING:

cv::FileStorage fp("depth_file.xml", cv::FileStorage::WRITE);
fp << "dframe" << dframe;
fp.release();

READING:

cv::FileStorage fs(dframeName, cv::FileStorage::READ);
if( fs.isOpened() == false)
{
    cerr<< "No More....Quitting...!";
    return 0;
}
fs["dframe"] >> dframe;