Detecting edges and corners using morphological filters

Morphological filters can also be used to detect specific features in an image. In this recipe, we will learn how to detect contours and corners in a gray-level image.

Getting ready

In this recipe, the following image will be used:

How to do it...

The edges of an image can be detected by using the appropriate filter of the cv::morphologyEx function. Refer to the following code:

// Get the gradient image using a 3x3 structuring element
cv::Mat result;
cv::morphologyEx(image,result,
                         cv::MORPH_GRADIENT,cv::Mat());

// Apply threshold to obtain a binary image
int threshold= 40;
cv::threshold(result, result, 
                    threshold, 255, cv::THRESH_BINARY);

The following image is obtained as the result:

In order to detect corners using morphology, we now define a class named MorphoFeatures as follows:

class MorphoFeatures {

  private:

     // threshold to produce binary image
    int threshold;
    // structuring...