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70 Chapter 2 ■ Edge-Detection Techniques

for (i=0; i<WIDTH; i++)
for (j=0; j<im->info->nc; j++)
im->data[i][j] = 255;

for (i=im->info->nr-1; i>im->info->nr-1-WIDTH; i--)
for (j=0; j<im->info->nc; j++)
im->data[i][j] = 255;

for (i=0; i<im->info->nr; i++)
for (j=0; j<WIDTH; j++)
im->data[i][j] = 255;

for (i=0; i<im->info->nr; i++)
for (j=im->info->nc-WIDTH-1; j<im->info->nc; j++)
im->data[i][j] = 255;

display_image (im);
save_image (im, “canny.jpg“);
return 0;
}

2.10 Source Code for the Shen-Castan

Edge Detector

/* ISEF edge detector */
#include “stdio.h“
#include “cv.h“
#include “highgui.h“
#include <stdio.h>
#include <string.h>
#include <math.h>
#define OUTLINE 25

/* globals for shen operator */
double b = 0.9; /* smoothing factor 0 < b < 1 */
double low_thresh=20, high_thresh=22; /* threshold for hysteresis */
double ratio = 0.99;
int window_size = 7;
int do_hysteresis = 1;
float **lap; /* keep track of laplacian of image */
int nr, nc; /* nrows, ncols */
IMAGE edges; /* keep track of edge points (thresholded)