title: "OpenCV Error: The function/feature is not implemented" on Android app
body: <p>I am working with OpenCV (version 3.2) on an Native Android app using ndk-build.
  I got an error that I cannot get around.</p>
  
  <pre><code>E/cv::error(): OpenCV Error: The function/feature is not implemented (Unknown/unsupported array type) in int cv::_InputArray::type(int) const, file /build/master_pack-android/opencv/modules/core/src/matrix.cpp, line 1931
  A/libc: Fatal signal 6 (SIGABRT) at 0x00001f38 (code=-6), thread 8011 (CameraHandlerTh)
  </code></pre>
  
  <p>By using the debugger I found the code part that throws this error.
  <code>cv::findHomography();</code></p>
  
  <pre><code>void Homography33::compute() {
    if ( valid ) return;
  
    std::vector&lt;cv::Point2f&gt; sPts;
    std::vector&lt;cv::Point2f&gt; dPts;
    for (int i=0; i&lt;4; i++) {
      sPts.push_back(cv::Point2f(srcPts[i].first, srcPts[i].second));
    }
    for (int i=0; i&lt;4; i++) {
      dPts.push_back(cv::Point2f(dstPts[i].first - cxy.first, dstPts[i].second - cxy.second));
    }
    cv::Mat homography = cv::findHomography(sPts, dPts); // throws error
    for (int c=0; c&lt;3; c++) {
      for (int r=0; r&lt;3; r++) {
        H(r,c) = homography.at&lt;double&gt;(r,c);
      }
    }
  
    valid = true;
  }
  </code></pre>
  
  <p>Any idea ?</p>
  
  <p>Thanks in advance,</p>