def medianFilter(source1, dest, k):
  w = pmGetImageWidth(dest)
  h = pmGetImageHeight(dest)
  k2 = k/2
  for x in range(w):
    for y in range(h):
      # Pull out vector to be sorted.
      xstart = max(0, x-k2) # Be careful at the border
      ystart = max(0, y-k2)
      xend = min(w, xstart+k)
      yend = min(h, ystart+k)
      neighbors = []
      for xx in range(xstart, xend):
        for yy in range(ystart, yend):
          neighbors.append(pmGetPixel(source1, xx, yy)[0])
      index_of_median = len(neighbors)/2
      neighbors.sort()
      median = neighbors[index_of_median]
      pmSetPixel(dest, x, y, median, median, median)

# An example call to filter the image in window 1,
# putting the result in window 2, using a 3x3 neighborhood:
medianFilter(1, 2, 3)