Merge pull request #455 from zivy/bugSurfaceHausdorffDistance

BUG: issue when segmentation touched the image border

Author: zivy

Python/34_Segmentation_Evaluation.ipynb

@@ -490,6 +490,18 @@
     "    \"\"\"\n",
     "    Compute symmetric surface distances and take the maximum.\n",
     "    \"\"\"\n",
+    "    # When the segmentation touches the image border we have corner case for the computation.\n",
+    "    # The surface/contour computation yields a surface that is outside the image bounds and\n",
+    "    # is thus not included in the computation. This is not correct for our use case. By padding\n",
+    "    # the segmentations we ensure that we obtain the surface as expected and the distance computations\n",
+    "    # are correct. Padding has no effect on results if the original segmentations did not touch the image\n",
+    "    # border.\n",
+    "    dim = reference_segmentation.GetDimension()\n",
+    "    reference_segmentation = sitk.ConstantPad(\n",
+    "        reference_segmentation, [1] * dim, [1] * dim\n",
+    "    )\n",
+    "    seg = sitk.ConstantPad(seg, [1] * dim, [1] * dim)\n",
+    "\n",
     "    reference_surface = sitk.LabelContour(reference_segmentation)\n",
     "    reference_distance_map = sitk.Abs(\n",
     "        sitk.SignedMaurerDistanceMap(\n",