Calling OpenCV C++ Code in C# Windows Form Applications

Some prerequisites are needed:

2. CUDA cuda_6.5.14_windows_general_64

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

Choose DLL

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

CVision.h

CVision.cpp

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

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

G:\CSharp\MyToolkitd\Release

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

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

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

and using CVision namespace also

   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.

References:

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