Canny edge detection in images

Edge detection is the foundation practice with Computer Vision. To detect edges OpenCV has cvCanny function.

Syntax

void cvCanny(const CvArr* image, CvArr* edges, double threshold1, double threshold2, int aperture size=3 );

Parameters :

edges Single-channel image to store the edges found by the function
threshold1 The first threshold
threshold2 The second threshold.
aperture size Aperture parameter for the Sobel operator.

Example

#include "cv.h"
#include "highgui.h"

int main( int argc, char** argv )
{
  IplImage* img_rgb = cvLoadImage("Desert1.jpg");
  // create another image
  IplImage* img_gry = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ),
                                     img_rgb->depth, 1);
  // convert rgb to gray
  cvCvtColor(img_rgb, img_gry ,CV_BGR2GRAY);
  // initialize windows to show image
  cvNamedWindow("Gray Image", CV_WINDOW_AUTOSIZE );
  cvNamedWindow("Canny Edge Detector", CV_WINDOW_AUTOSIZE );
  cvShowImage("Gray Image", img_gry );

  // Canny Edge Detector
  cvCanny( img_gry, img_gry, 10, 100, 3);

  cvShowImage("Canny Edge Detector", img_gry);
  cvWaitKey(0);
  cvReleaseImage( &img_rgb);
  cvReleaseImage( &img_gry);
  cvDestroyWindow("Gray Image");
  cvDestroyWindow("Canny Edge Detector");
}