/* BWlabel
label groups of 4-connected pixels.
This is an implementation of the Matlab function bwlabel
*/
unsigned long bwlabel(ImageMatrix &Im, int level) {
long x, y, base_x,base_y,stack_count, w = Im.width, h = Im.height;
unsigned long group_counter = 1;
point *stack=new point[w*h];
pixData &pix_plane = Im.WriteablePixels();
for (y = 0; y < h; y++) {
for (x = 0; x < w; x++) {
if ( pix_plane(y,x) == 1) {
/* start a new group */
group_counter++;
pix_plane(y,x) = group_counter;
stack[0].x=x;
stack[0].y=y;
stack_count=1;
while (stack_count > 0) {
base_x=stack[0].x;
base_y=stack[0].y;
if (base_x > 0 && pix_plane(base_y,base_x-1) == 1) {
pix_plane(base_y,base_x-1) = group_counter;
stack[stack_count].x=base_x-1;
stack[stack_count].y=base_y;
stack_count++;
}
if (base_x < w-1 && pix_plane(base_y,base_x+1) == 1) {
pix_plane(base_y,base_x+1) = group_counter;
stack[stack_count].x=base_x+1;
stack[stack_count].y=base_y;
stack_count++;
}
if (base_y > 0 && pix_plane(base_y-1,base_x) == 1) {
pix_plane(base_y-1,base_x) = group_counter;
stack[stack_count].x=base_x;
stack[stack_count].y=base_y-1;
stack_count++;
}
if (base_y < h-1 && pix_plane(base_y+1,base_x) == 1) {
pix_plane(base_y+1,base_x) = group_counter;
stack[stack_count].x=base_x;
stack[stack_count].y=base_y+1;
stack_count++;
}
/* look for 8 connected pixels */
if (level==8) {
if (base_x > 0 && base_y > 0 && pix_plane(base_y-1,base_x-1) == 1) {
pix_plane(base_y-1,base_x-1) = group_counter;
stack[stack_count].x=base_x-1;
stack[stack_count].y=base_y-1;
stack_count++;
}
if (base_x < w-1 && base_y > 0 && pix_plane(base_y-1,base_x+1) == 1) {
pix_plane(base_y-1,base_x+1) = group_counter;
stack[stack_count].x=base_x+1;
stack[stack_count].y=base_y-1;
stack_count++;
}
if (base_x > 0 && base_y < h-1 && pix_plane(base_y+1,base_x-1) == 1) {
pix_plane(base_y+1,base_x-1) = group_counter;
stack[stack_count].x=base_x-1;
stack[stack_count].y=base_y+1;
stack_count++;
}
if (base_x < w-1 && base_y < h-1 && pix_plane(base_y+1,base_x+1) == 1) {
pix_plane(base_y+1,base_x+1) = group_counter;
stack[stack_count].x=base_x+1;
stack[stack_count].y=base_y+1;
stack_count++;
}
}
stack_count-=1;
memmove(stack,&(stack[1]),sizeof(point)*stack_count);
}
}
}
}
/* now decrease every non-zero pixel by one because the first group was "2" */
for (y=0;y<h;y++)
for (x=0;x<w;x++)
if (pix_plane(y,x) != 0)
pix_plane(y,x) -= 1;
delete [] stack;
return(group_counter-1);
}
