Question

In the following code I want to use the dilate function but I don’t know how to cast a Mat class into a InputArray and OutputArray. Can you help me?

Using this prototype function:

void dilate(InputArray src, OutputArray dst, InputArray kernel, Point anchor=Point(-1,-1), int iterations=1, int borderType=BORDER_CONSTANT, const Scalar& borderValue=morphologyDefaultBorderValue() )

Here’s my code:

#include "opencv2/opencv.hpp"

using namespace cv;

int main(int, char**)
{
    Mat edges;

    VideoCapture cap(0); // open the default camera
    if(!cap.isOpened())  // check if we succeeded
        return -1;


    for(;;)
    {

        Mat frame;
        cap >> frame; // get a new frame from camera
        cvtColor(frame, edges, CV_BGR2GRAY);
        GaussianBlur(edges, edges, Size(7,7), 1.5, 1.5);
        //dilate(edges,edges,NULL);
        Canny(edges, edges, 0, 30, 3);
        imshow("edges", frame);
        if(waitKey(30) >= 0) break;
    }
    // the camera will be deinitialized automatically in VideoCapture destructor
    return 0;
}

Answer 1

There are examples all around Stack Overflow, like this:

int erosion_size = 6;   
cv::Mat element = cv::getStructuringElement(cv::MORPH_CROSS,
                      cv::Size(2 * erosion_size + 1, 2 * erosion_size + 1), 
                      cv::Point(erosion_size, erosion_size) );

cv::dilate(edges, edges, element); 

Or this:

cv::dilate(edges, edges, cv::Mat(), cv::Point(-1,-1));