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Before you start to read this article, you should have read VS2013 Build OpenCV2.4.9 with CUDA.

Some prerequisites are needed:

1.  Visual C++ Redistributable Packages for Visual Studio 2013

2.  CUDA  cuda_6.5.14_windows_general_64

3. OpenCV 2.4.9

4. Intel TBB  tbb43_20150316oss

 

Here are two sample codes, one is written in C++ dll project(CVision) and the other one is a C# windows form program(CVisionClient)

Now I am going to create a new Visual C++ dll project

image

Choose DLL

image

Remember to build with x64 platform for this project, otherwise there will be an error something like “external function” cannot be found

image

CVision.h

image

CVision.cpp

image

Let’s take a look in imread, which passes an image filename to the subroutine

   1: bool ImageProc::imread(wchar_t* txt)
   2: {        
   3:     wstring ws(txt);
   4:     filename = WstringToString(ws);
   5:     image = cv::imread( filename );
   6:     if( !image.data)
   7:     {
   8:         return false;
   9:     }
  10:     else
  11:     {
  12:         return true;
  13:     }        
  14:     return true;
  15: }

One thing should be take care is wide string to string conversion, which is done by WstringToString function. 

   1: std::string WstringToString(const std::wstring str)
   2: {   
   3:     unsigned len = str.size() * 4;
   4:     setlocale(LC_CTYPE, "cht");
   5:     char *p = new char[len];
   6:     wcstombs(p,str.c_str(),len);
   7:     std::string str1(p);
   8:     delete[] p;
   9:     return str1;
  10: }

And we display image by another function named showImage

   1: void ImageProc::showImage()
   2: {
   3:     namedWindow( filename, CV_WINDOW_NORMAL );
   4:     imshow(filename, image );
   5: }

Finally don’t forget to select CLR supported, and the C++ dll can be called by C# applications

image

CVision.dll will be created in the directory shown below if your compiled successfully.

G:\CSharp\MyToolkit\x64\Release

image

=======================================================

Now we are ready to create a C# Windows form application

image

Now we’re going to add a reference to CVision.dll

image

and using CVision namespace also

image

   1: private void ToolStripMenuItem_Click(object sender, EventArgs e)
   2:         {
   3:             OpenFileDialog openFileDialog1 = new OpenFileDialog();
   4:             openFileDialog1.InitialDirectory = "c:\\";
   5:             openFileDialog1.Filter = "jpg files (*.jpg)|*.jpg|bmp files (*.bmp)|*.bmp|png files (*.png)|*.png";
   6:             openFileDialog1.FilterIndex = 0;
   7:             openFileDialog1.RestoreDirectory = true;
   8:             if (openFileDialog1.ShowDialog() == DialogResult.OK)
   9:             {
  10:                 try
  11:                 {
  12:                     ImageProc ip = new ImageProc();
  13:                     unsafe
  14:                     {
  15:                         byte[] buf = Encoding.Unicode.GetBytes(openFileDialog1.FileName);
  16:                         
  17:                         fixed (byte* p = &buf[0] )
  18:                         {                                                        
  19:                             if( ip.imread((char *)p))
  20:                                 ip.showImage();                            
  21:                         }            
  22:                                              
  23:                     }                             
  24:                 }
  25:                 catch (Exception ex)
  26:                 {
  27:                     MessageBox.Show("Error: Could not read file from disk. Original error: " + ex.Message);
  28:                 }
  29:             }
  30:         }

In the following picture, you can see that the path of input image including traditional Chinese characters that does not cause any problem.

image

 

 

References:

C# and the char* mess

wstring与string相互转换

Conversion of wchar_t* to string [duplicate]

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