How to crop away convexity defects?

Question

I\'m trying to detect and fine-locate some objects in images from contours. The contours that I get often include some noise (maybe form the background, I don\'t know). The

Answer 1

As a starting point and assuming the defects are never too big relative to the object you are trying to recognize, you can try a simple erode+dilate strategy before using cv::matchShapes as shown below.

 int max = 40; // depending on expected object and defect size
 cv::Mat img = cv::imread("example.png");
 cv::Mat eroded, dilated;
 cv::Mat element = cv::getStructuringElement(cv::MORPH_ELLIPSE, cv::Size(max*2,max*2), cv::Point(max,max));
 cv::erode(img, eroded, element);
 cv::dilate(eroded, dilated, element);
 cv::imshow("original", img);
 cv::imshow("eroded", eroded);
 cv::imshow("dilated", dilated);