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Chapter 2 ■ Edge-Detection Techniques 69

int main ()
{
int i,j;
float s=1.0;
int low= 0,high=-1;
FILE *params;
IMAGE im, magim, oriim;
char name[128];

// Try to read an image
printf (“Enter path to the image file to be processed: “);
scanf (“%s“, name);
printf (“Opening file '%s’\n“, name);

/* Read parameters from the file canny.par */
params = fopen (“canny.par“, “r“);
if (params)
{
fscanf (params, “%d“, &low); /* Lower threshold */
fscanf (params, “%d“, &high); /* High threshold */
fscanf (params, “%f“, &s); /* Gaussian standard deviation */
printf (“Parameters from canny.par: HIGH: %d LOW %d Sigma %f\n“,
high, low, s);
fclose (params);
}
else printf (“Parameter file 'canny.par' does not exist.\n“);
im = get_image(name);
display_image (im);

/* Create local image space */
magim = newimage (im->info->nr, im->info->nc);
if (magim == NULL)
{
printf (“Out of storage: Magnitude\n“);
exit (1);
}

oriim = newimage (im->info->nr, im->info->nc);
if (oriim == NULL)
{
printf (“Out of storage: Orientation\n“);
exit (1);
}

/* Apply the filter */
canny (s, im, magim, oriim);

/* Hysteresis thresholding of edge pixels */
hysteresis (high, low, im, magim, oriim);