Fix NLST keypoint warping coordinates

Author: hmeixx

3d_registration/learn2reg_nlst_paired_lung_ct.ipynb

@@ -660,11 +660,15 @@
     "    # warp vectors for keypoints (optional)\n",
     "    if fixed_keypoints is not None:\n",
     "        with torch.no_grad():\n",
-    "            offset = torch.as_tensor(fixed_image.shape[-3:]).to(fixed_keypoints.device) / 2\n",
+    "            offset = (torch.as_tensor(fixed_image.shape[-3:]).to(fixed_keypoints.device) - 1) / 2\n",
     "            offset = offset[None][None]\n",
     "            ddf_keypoints = torch.flip((fixed_keypoints - offset) / offset, (-1,))\n",
     "        ddf_keypoints = (\n",
-    "            F.grid_sample(ddf_image, ddf_keypoints.view(batch_size, -1, 1, 1, 3))\n",
+    "            F.grid_sample(\n",
+    "                ddf_image,\n",
+    "                ddf_keypoints.view(batch_size, -1, 1, 1, 3),\n",
+    "                align_corners=True,\n",
+    "            )\n",
     "            .view(batch_size, 3, -1)\n",
     "            .permute((0, 2, 1))\n",
     "        )\n",