Using Erode and Dilate in Emgu (OpenCV for C#)

Question

Unlike the python bindings for the OpenCv Dilate function, the C# version has more arguments that are all mandatory, and I'm not sure what to use for the elements for the element argument. I tried the following, and the output looks identical to the inpur:

public static void Dilate(
    IInputArray src,
    IOutputArray dst,
    IInputArray element,
    Point anchor,
    int iterations,
    BorderType borderType,
    MCvScalar borderValue
)

In Python I would do something like:

kernel = np.ones((5,5),np.uint8)

dilation = cv2.dilate(src, kernel,iterations=3)

In C#, I tried using the Default values. but the output does not look any different than the input.

    ScalarArray elem = new ScalarArray(0);

    CvInvoke.Dilate(_cannyFrame
             , _dilatedCanny
             , elem
             , new Point(-1,- 1)
             , 6
             , BorderType.Constant 
             , new MCvScalar(255, 255, 255) );    

Answer 1

The error seems to be in the structuring element. You are using an elem equal to zero and this has no effect on destination image _dilatedCanny . In python you are using a kernel with ones element...

Answer 2

Try this

Mat element = CvInvoke.GetStructuringElement(Emgu.CV.CvEnum.ElementShape.Rectangle, new Size(3, 3), new Point(-1, -1));

CvInvoke.Dilate(_cannyFrame
         , _dilatedCanny
         , element 
         , new Point(-1,- 1)
         , 6
         , BorderType.Constant 
         , new MCvScalar(255, 255, 255) );