canny-operator

I'm using a project using OpenCV for detecting a card that will be place on a atable. I have successfully detect it using Canny Edge. However, for different image the parameter must be tuned manually. I wish for my project to be worked with every image without manually tune the parameter. What Should I do? Balaji R If your image consist of Distinct Background & Foreground, You can get the threshold for that automatically as follows explained in this paper http://www.academypublisher.com/proc/isip09/papers/isip09p109.pdf . Compute Otsu's threshold + Binary threshold for your image. Use the Otsu

I have a canny edge image I want to remove all line except the lines that look like a semi-circle/ellipse or a 'C'. Tried Hough Circle transforms, it detects all curves.Don't need that. A simple approach would be: Find connected components Find the minimum oriented bounding box Compute the aspect ratio of the box, and check if it's too much elongated . On your image, I marked in red almost straight lines, and in green the curved lines. You can play with the threshold on the aspect ratio: Code: #include<opencv2/opencv.hpp> using namespace cv; int main() { // Load image Mat1b img = imread("path