/*******************************************************************************
* This function is to be called by a pthread in order to perform this action
* alongside the main functionality, and not halt it.
*******************************************************************************/
void* radian_thread_function(void *arg)
{
short int *delta_x; /* The first devivative image, x-direction. */
short int *delta_y; /* The first devivative image, y-direction. */
int rows;
int cols;
float *dir_radians = NULL; /* Gradient direction image. */
char *fname;
FILE *fpdir = NULL; /* File to write the gradient image to. */
delta_x = ((thread_args_t *)arg)->delta_x;
delta_y = ((thread_args_t *)arg)->delta_y;
rows = ((thread_args_t *)arg)->rows;
cols = ((thread_args_t *)arg)->cols;
fname = ((thread_args_t *)arg)->fname;
/*************************************************************************
* Compute the direction up the gradient, in radians that are
* specified counteclockwise from the positive x-axis.
*************************************************************************/
radian_direction(delta_x, delta_y, rows, cols, &dir_radians, -1, -1);
/*************************************************************************
* Write the gradient direction image out to a file.
*************************************************************************/
if((fpdir = fopen(fname, "wb")) == NULL){
fprintf(stderr, "Error opening the file %s for writing.\n", fname);
pthread_exit(NULL); //probably should put an error code or something...
}
fwrite(dir_radians, sizeof(float), rows*cols, fpdir);
fclose(fpdir);
free(dir_radians);
printf("Thread got to the endo ;).\n");
pthread_exit(NULL);
}
/*******************************************************************************
* PROCEDURE: canny
* PURPOSE: To perform canny edge detection.
* NAME: Mike Heath
* DATE: 2/15/96
*******************************************************************************/
void canny(unsigned char *image, int rows, int cols, float sigma,
float tlow, float thigh, unsigned char **edge, char *fname)
{
FILE *fpdir=NULL; /* File to write the gradient image to. */
unsigned char *nms; /* Points that are local maximal magnitude. */
short int *smoothedim, /* The image after gaussian smoothing. */
*delta_x, /* The first devivative image, x-direction. */
*delta_y, /* The first derivative image, y-direction. */
*magnitude; /* The magnitude of the gadient image. */
float *dir_radians=NULL; /* Gradient direction image. */
/****************************************************************************
* Perform gaussian smoothing on the image using the input standard
* deviation.
****************************************************************************/
if(VERBOSE) printf("Smoothing the image using a gaussian kernel.\n");
smoothedim = gaussian_smooth(image, rows, cols, sigma);
/****************************************************************************
* Compute the first derivative in the x and y directions.
****************************************************************************/
if(VERBOSE) printf("Computing the X and Y first derivatives.\n");
derrivative_x_y(smoothedim, rows, cols, &delta_x, &delta_y);
/****************************************************************************
* This option to write out the direction of the edge gradient was added
* to make the information available for computing an edge quality figure
* of merit.
****************************************************************************/
if(fname != NULL)
{
/*************************************************************************
* Compute the direction up the gradient, in radians that are
* specified counteclockwise from the positive x-axis.
*************************************************************************/
radian_direction(delta_x, delta_y, rows, cols, &dir_radians, -1, -1);
/*************************************************************************
* Write the gradient direction image out to a file.
*************************************************************************/
if((fpdir = fopen(fname, "wb")) == NULL)
{
fprintf(stderr, "Error opening the file %s for writing.\n", fname);
exit(1);
}
fwrite(dir_radians, sizeof(float), rows*cols, fpdir);
fclose(fpdir);
free(dir_radians);
}
/****************************************************************************
* Compute the magnitude of the gradient.
****************************************************************************/
/****************************************************************************
* Allocate an image to store the magnitude of the gradient.
****************************************************************************/
if((magnitude = (short *) malloc(rows*cols* sizeof(short))) == NULL)
{
fprintf(stderr, "Error allocating the magnitude image.\n");
exit(1);
}
if(VERBOSE) printf("Computing the magnitude of the gradient.\n");
magnitude_x_y(delta_x, delta_y, rows, cols, magnitude);
/****************************************************************************
* Perform non-maximal suppression.
****************************************************************************/
if(VERBOSE) printf("Doing the non-maximal suppression.\n");
if((nms = (unsigned char *) malloc(rows*cols*sizeof(unsigned char)))==NULL)
{
fprintf(stderr, "Error allocating the nms image.\n");
exit(1);
}
non_max_supp(magnitude, delta_x, delta_y, rows, cols, nms);
/****************************************************************************
* Use hysteresis to mark the edge pixels.
****************************************************************************/
if(VERBOSE) printf("Doing hysteresis thresholding.\n");
if( (*edge=(unsigned char *)malloc(rows*cols*sizeof(unsigned char))) == NULL )
{
fprintf(stderr, "Error allocating the edge image.\n");
exit(1);
}
apply_hysteresis(magnitude, nms, rows, cols, tlow, thigh, *edge);
/****************************************************************************
* Free all of the memory that we allocated except for the edge image that
* is still being used to store out result.
****************************************************************************/
free(smoothedim);
free(delta_x);
free(delta_y);
free(magnitude);
free(nms);
}
