Catatan Fahmi Lembaran ilmu dan cerita pengalaman

Let’s try to detect corner from an image.
In this sample, I am using my own picture = building.jpg.
You can edit the below source code and try to detect corner from different image.

I am implementing two types of function to detect corner :
1. cvCornerMinEigenVal
The function cvCornerMinEigenVal is to calculate and store the minimal eigen value of derivative covariation matrix for every pixel, i.e. min(λ1, λ2) in terms of the previous function.

2. cvCornerHarris
Harris edge detector. You can refer to the original paper = A Combined Corner and Edge Detector

You may also refer to the next article : click here (Harris Corner Detection).

Source code :

#include <stdio.h>
#include <cv.h>
#include <highgui.h>

int main (void)
{
	int i, corner_count = 150;
	IplImage *dst_img1, *dst_img2, *src_img_gray;
	IplImage *eig_img, *temp_img;
	CvPoint2D32f *corners;

	//image file
	char imagePath[256] = "c:\\images\\building.jpg";
	printf("%s\n", imagePath);

	dst_img1 = cvLoadImage (imagePath, CV_LOAD_IMAGE_ANYCOLOR | CV_LOAD_IMAGE_ANYDEPTH);
	dst_img2 = cvCloneImage (dst_img1);
	src_img_gray = cvLoadImage (imagePath, CV_LOAD_IMAGE_GRAYSCALE);
	eig_img = cvCreateImage (cvGetSize (src_img_gray), IPL_DEPTH_32F, 1);
	temp_img = cvCreateImage (cvGetSize (src_img_gray), IPL_DEPTH_32F, 1);
	corners = (CvPoint2D32f *) cvAlloc (corner_count * sizeof (CvPoint2D32f));

	// (1)Corner detection using cvCornerMinEigenVal
	cvGoodFeaturesToTrack (src_img_gray, eig_img, temp_img, corners, &corner_count, 0.1, 15);
	cvFindCornerSubPix (src_img_gray, corners, corner_count,
					  cvSize (3, 3), cvSize (-1, -1), cvTermCriteria (CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.03));
	// (2)Draw the detected corner
	for (i = 0; i < corner_count; i++)
	cvCircle (dst_img1, cvPointFrom32f (corners[i]), 3, CV_RGB (255, 0, 0), 2);

	//Message for debugging
	printf("MinEigenVal corner count = %d\n", corner_count);

	// (3)Corner detection using cvCornerHarris
	corner_count = 150;
	cvGoodFeaturesToTrack (src_img_gray, eig_img, temp_img, corners, &corner_count, 0.1, 15, NULL, 3, 1, 0.01);
	cvFindCornerSubPix (src_img_gray, corners, corner_count,
					  cvSize (3, 3), cvSize (-1, -1), cvTermCriteria (CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.03));
	// (4)Draw the detected corner
	for (i = 0; i < corner_count; i++)
	cvCircle (dst_img2, cvPointFrom32f (corners[i]), 3, CV_RGB (0, 0, 255), 2);

	//Message for debugging
	printf("Harris corner count = %d\n", corner_count);

	// (5)Display the result
	cvNamedWindow ("EigenVal", CV_WINDOW_AUTOSIZE);
	cvShowImage ("EigenVal", dst_img1);
	cvNamedWindow ("Harris", CV_WINDOW_AUTOSIZE);
	cvShowImage ("Harris", dst_img2);
	cvWaitKey (0);

	cvDestroyWindow ("EigenVal");
	cvDestroyWindow ("Harris");
	cvReleaseImage (&dst_img1);
	cvReleaseImage (&dst_img2);
	cvReleaseImage (&eig_img);
	cvReleaseImage (&temp_img);
	cvReleaseImage (&src_img_gray);

	return 0;
}

Result :