/// <summary>
/// Label the connected components of an image.
/// </summary>
public static int label_components(ref Intarray image, bool four_connected = false)
{
int w = image.Dim(0), h = image.Dim(1);
// We slice the image into columns and call make_set()
// for every continuous segment within each column.
// Maximal number of segments per column is (h + 1) / 2.
// We do it `w' times, so it's w * (h + 1) / 2.
// We also need to add 1 because index 0 is not used, but counted.
UnionFind uf = new UnionFind(w * (h + 1) / 2 + 1);
uf.make_set(0);
int top = 1;
for (int i = 0; i < image.Length1d(); i++)
{
image.Put1d(i, (image.At1d(i) > 0 ? 1 : 0));
}
//for(int i=0;i<w;i++) {image(i,0) = 0; image(i,h-1) = 0;}
//for(int j=0;j<h;j++) {image(0,j) = 0; image(w-1,j) = 0;}
for (int i = 0; i < w; i++)
{
int current_label = 0;
for (int j = 0; j < h; j++)
{
int pixel = image[i, j];
int range = four_connected ? 0 : 1;
for (int delta = -range; delta <= range; delta++)
{
int adj_label = NarrayUtil.Bat(image, i - 1, j + delta, 0);
if (pixel == 0)
{
current_label = 0;
continue;
}
if (current_label == 0)
{
current_label = top;
uf.make_set(top);
top++;
}
if (adj_label > 0)
{
current_label = uf.find_set(current_label);
adj_label = uf.find_set(adj_label);
if (current_label != adj_label)
{
uf.make_union(current_label, adj_label);
current_label = uf.find_set(current_label);
adj_label = uf.find_set(adj_label);
}
}
image[i, j] = current_label;
}
}
}
for (int i = 0; i < image.Length1d(); i++)
{
if (image.At1d(i) == 0)
{
continue;
}
image.Put1d(i, uf.find_set(image.At1d(i)));
}
return(renumber_labels(image, 1));
}