OpenCv c ++为基本的打印垫功能创建一个C包装器？

Question

I can create and print a matrix like this:

  Mat M(2,2, CV_8UC3, Scalar(0,0,255));
 cout << "M = " << endl << " " << M << endl << endl;

My C wrapper for the C++ functions is this:

Mat* cv_printmat(Mat* mat) {

   return  cout << "Matrix = " << endl << " " << *mat << endl << endl;
    }

Not sure where to go from here...I need to declare "Mat* mat" as is ...an opaque pointer for my purpose...but getting this error

       In file included from /usr/include/c++/4.8/ios:44:0,
             from /usr/include/c++/4.8/istream:38,
             from /usr/include/c++/4.8/sstream:38,
             from /usr/include/c++/4.8/complex:45,
             from /usr/local/include/opencv2/core/cvstd.inl.hpp:48,
             from /usr/local/include/opencv2/core.hpp:1256,
             from /usr/local/include/opencv2/opencv.hpp:46,
             from opencv_generated.hpp:1,
             from cl-opencv-glue.cpp:1:
/usr/include/c++/4.8/bits/basic_ios.h:115:7: note: 
candidate is: std::basic_ios<_CharT, _Traits>::operator 
void*() const [with _CharT = char; _Traits = std::
char_traits<char>] <near match>
   operator void*() const
   ^
/usr/include/c++/4.8/bits/basic_ios.h:115:7: note:   
no known conversion for implicit ‘this’ parameter from ‘void*’ to ‘cv::Mat*’

compiling with this:

 g++ -Wall -shared -fPIC -o libcl-opencv-glue.so cl-opencv-glue.cpp

any help is much appreciated=).

Edit...new error

 opencv-glue.cpp :150:58 error:invalid user-defined conversion from                 
‘std::basic_ostream<char>::__ostream_type {aka std
::basic_ostream<char>}’ to ‘cv::Mat*’ [-fpermissive]
     return cout << "M = " << endl << " " << *mat << endl << endl;
                                                          ^
      In file included from /usr/include/c++/4.8/ios:44:0,
                 from /usr/include/c++/4.8/istream:38,
                 from /usr/include/c++/4.8/sstream:38,
                 from /usr/include/c++/4.8/complex:45,
                 from /usr/local/include/opencv2/core/cvstd.inl.hpp:48,
                 from /usr/local/include/opencv2/core.hpp:1256,
                 from /usr/local/include/opencv2/opencv.hpp:46,
                 from opencv_generated.hpp:1,
                 from opencv-glue.cpp:1:
/usr/include/c++/4.8/bits/basic_ios.h:115:7: note: candidate is: 
std::basic_ios<_CharT, _Traits>::operator void*() const [with _
CharT = char; _Traits = std::char_traits<char>] <near match>
       operator void*() const
       ^
/usr/include/c++/4.8/bits/basic_ios.h:115:7: note:   
no known conversion for implicit ‘this’ parameter from 
‘void*’ to ‘cv::Mat*’

Answer 1

Your return data type is cv::Mat*, whereas the return data type for std::cout is void*. Not sure what your goal is, but this should compile if you are just trying to print.

void cv_printmat(Mat* mat) {
  cout << "Matrix = " << endl << " " << *mat << endl << endl;
}

int main(int argc, char* argv[]){
   cv::Mat M(2,2, CV_8UC3, cv::Scalar(0,0,255));
   cv_printmat(&M);
}