Automatic calculation of low and high thresholds for the Canny operation in opencv

Question

In openCV, the low and high thresholds for the canny operator are mandatory:

cvCanny(input,output,thresh1,thresh2)

In Matlab, there\'s an o

Answer 1

As Luca Del Tongo has suggested, you can calculate the thresholds from the grey image, e.g. in Java using OpenCV...

MatOfDouble mu = new MatOfDouble();
MatOfDouble stddev = new MatOfDouble();
Core.meanStdDev(greyMat, mu, stddev);
threshold1 = mu.get(0, 0)[0];
threshold2 = stddev.get(0, 0)[0];
Imgproc.Canny(greyMat, outputMat, threshold1, threshold2);