void
frame_t::convert_grayscale()
{
int i;
for (i=0; i<n_img(); i++) {
convert_grayscale (i);
}
}
void
detect_edges(Image *img, float sigma, float threshold, \
unsigned char *edge_pix, PList *edge_pts)
{
int x, y;
int w = img->w;
int h = img->h;
// convert image to grayscale
float **gray = array_create(w, h);
convert_grayscale(img, gray);
// blur grayscale image
float **gray2 = array_create(w, h);
gaussian_blur(gray, gray2, w, h, sigma);
// compute gradient of blurred image
float **g_mag = array_create(w, h);
float **g_ang = array_create(w, h);
compute_gradient(gray2, w, h, g_mag, g_ang);
// mark edge pixels
#define PIX(y,x) edge_pix[(y)*w+(x)]
#pragma omp parallel
{
#pragma omp for private(x) nowait
for (y = 0; y < h; y++)
for (x = 0; x < w; x++)
{
PIX(y,x) = is_edge(g_mag,g_ang,threshold,x,y,w,h) ? 255 : 0;
}
// connect horizontal edges
#pragma omp for private(x) nowait
for (y = 0; y < h ; y++)
for (x = 1; x < w-1; x++)
{
if (!PIX(y,x) && PIX(y,x+1) && PIX(y,x-1))
PIX(y,x) = 255;
}
// connect vertical edges
#pragma omp for private(y) nowait
for (x = 0; x < w ; x++)
for (y = 1; y < h-1; y++)
{
if (!PIX(y,x) && PIX(y+1,x) && PIX(y-1,x))
PIX(y,x) = 255;
}
#pragma omp for private(x)
// connect diagonal edges
for (y = 1; y < h-1; y++)
for (x = 1; x < w-1; x++)
{
if (!PIX(y,x) && PIX(y-1,x-1) && PIX(y+1,x+1))
PIX(y,x) = 255;
if (!PIX(y,x) && PIX(y-1,x+1) && PIX(y+1,x-1))
PIX(y,x) = 255;
}
}
// add edge points to list
if (edge_pts)
{
for (y = 0; y < h; y++)
for (x = 0; x < w; x++)
{
if (PIX(y,x)) PList_push(edge_pts, x, y);
}
}
// cleanup
array_free(g_mag, h);
array_free(g_ang, h);
array_free(gray2, h);
array_free(gray, h);
}