Adaptive parameter for Canny Edge

Question

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?

Answer 1

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.

1. Compute Otsu's threshold + Binary threshold for your image.
2. Use the Otsu's threshold value as higher threshold for Canny's algorithm.

CODE:

Mat mCanny_Gray,mThres_Gray;
Mat mSrc_Gray=imread("Test.bmp",0);

double CannyAccThresh = threshold(mSrc_Gray,mThres_Gray,0,255,CV_THRESH_BINARY|CV_THRESH_OTSU);

double CannyThresh = 0.1 * CannyAccThresh;

Canny(mSrc_Gray,mCanny_Gray,CannyThresh,CannyAccThresh);
imshow("mCanny_Gray",mCanny_Gray);

You can also refer this thread.