// geodesic dilation from markers
public static int[,] Reconstruction(int[,] markers, int[,] mask)
{
int[,] result = new int[markers.GetLength(0), markers.GetLength(1)];
DMaxHeap <Pixel> heap = new DMaxHeap <Pixel>(5);
// add markers to heap
for (int x = 0; x < markers.GetLength(0); x++)
{
for (int y = 0; y < markers.GetLength(1); y++)
{
if (markers[x, y] > 0 && mask[x, y] > 0)
{
Pixel p = new Pixel(x, y, Math.Min(markers[x, y], mask[x, y]));
heap.Add(p);
}
result[x, y] = 0;
}
}
// process heap in order of value
while (heap.Count > 0)
{
Pixel p = heap.Extract();
if (p.Value <= result[p.X, p.Y]) // not a higher value than already determined
{
continue;
}
result[p.X, p.Y] = p.Value;
// add neighbours
for (int i = -1; i <= 1; i++)
{
for (int j = -1; j <= 1; j++)
{
int pxx = p.X + i, pxy = p.Y + j;
if (pxx < 0 || pxx >= markers.GetLength(0) || pxy < 0 || pxy >= markers.GetLength(1)) // no pixel
{
continue;
}
int val = Math.Min(mask[pxx, pxy], p.Value);
if (val == result[pxx, pxy]) // no loops of pixels adding each other
{
continue;
}
heap.Add(new Pixel(pxx, pxy, val));
}
}
}
return(result);
}
// separate objects that are touching
public static bool[,] Watershed(int[,] image, decimal threshold)
{
bool[,] shed = new bool[image.GetLength(0), image.GetLength(1)]; // watershed mask
int[,] dt = DistanceTransform(image); // apply distance transform
int[,] dt2 = new int[dt.GetLength(0), dt.GetLength(1)];
// find global maximum
int max = int.MinValue;
for (int i = 0; i < dt.GetLength(0); i++)
{
for (int j = 0; j < dt.GetLength(1); j++)
{
max = Math.Max(max, dt[i, j]);
}
}
MPixel[,] pixels = new MPixel[dt.GetLength(0), dt.GetLength(1)]; // pixel object for each position
for (int i = 0; i < dt.GetLength(0); i++)
{
for (int j = 0; j < dt.GetLength(1); j++)
{
dt2[i, j] = dt[i, j] <= threshold * max ? 0 : dt[i, j]; // thresholded distance transform by parameter
}
}
List <Tuple <int, int> > maxima = GetLocalMaxima(dt2); // find maxima of thresholded dt
DMaxHeap <MPixel> heap = new DMaxHeap <MPixel>();
int label = 1;
foreach (Tuple <int, int> t in maxima) // start at maxima
{
MPixel p = new MPixel(t.Item1, t.Item2, label++, dt[t.Item1, t.Item2]);
heap.Add(p);
pixels[p.X, p.Y] = p;
}
while (heap.Count > 0)
{
MPixel p = heap.Extract();
int[] labels = new int[4]; // labels of neighbours
if (p.X > 0 && pixels[p.X - 1, p.Y] != null)
{
labels[0] = pixels[p.X - 1, p.Y].Label;
}
if (p.Y > 0 && pixels[p.X, p.Y - 1] != null)
{
labels[1] = pixels[p.X, p.Y - 1].Label;
}
if (p.X < pixels.GetLength(0) - 1 && pixels[p.X + 1, p.Y] != null)
{
labels[2] = pixels[p.X + 1, p.Y].Label;
}
if (p.Y < pixels.GetLength(1) - 1 && pixels[p.X, p.Y + 1] != null)
{
labels[3] = pixels[p.X, p.Y + 1].Label;
}
Array.Sort(labels);
int i = 0;
while (i < 4 && labels[i] == 0) // first neighbour label
{
i++;
}
bool same = true;
for (; i < 3; i++)
{
if (labels[i] != labels[i + 1]) // neighbours with different labels
{
same = false;
}
}
if (same && p.Label == 0) // all neighbour labels the same and current pixel's label not yet set
{
p.Label = labels[3]; // give the same label as neighbours
}
// add all unprocessed neighbours
MPixel newPixel;
if (p.X > 0 && pixels[p.X - 1, p.Y] == null)
{
newPixel = new MPixel(p.X - 1, p.Y, 0, dt[p.X - 1, p.Y]);
heap.Add(newPixel);
pixels[p.X - 1, p.Y] = newPixel;
}
if (p.Y > 0 && pixels[p.X, p.Y - 1] == null)
{
newPixel = new MPixel(p.X, p.Y - 1, 0, dt[p.X, p.Y - 1]);
heap.Add(newPixel);
pixels[p.X, p.Y - 1] = newPixel;
}
if (p.X < pixels.GetLength(0) - 1 && pixels[p.X + 1, p.Y] == null)
{
newPixel = new MPixel(p.X + 1, p.Y, 0, dt[p.X + 1, p.Y]);
heap.Add(newPixel);
pixels[p.X + 1, p.Y] = newPixel;
}
if (p.Y < pixels.GetLength(1) - 1 && pixels[p.X, p.Y + 1] == null)
{
newPixel = new MPixel(p.X, p.Y + 1, 0, dt[p.X, p.Y + 1]);
heap.Add(newPixel);
pixels[p.X, p.Y + 1] = newPixel;
}
}
// create mask from labels
for (int x = 0; x < shed.GetLength(0); x++)
{
for (int y = 0; y < shed.GetLength(1); y++)
{
shed[x, y] = pixels[x, y] == null || pixels[x, y].Label != 0;
}
}
return(shed);
}
