nodes: ImagePadForOutpaint: fix feathering, ignore edges not expanded

nodes.py

+import math
+
 import torch
 
 import os
@@ -942,28 +944,31 @@ class ImagePadForOutpaint:
             dtype=torch.float32,
         )
 
+        t = torch.zeros(
+            (d2, d3),
+            dtype=torch.float32
+        )
+
         if feathering > 0 and feathering * 2 < d2 and feathering * 2 < d3:
-            # distances to border
-            mi, mj = torch.meshgrid(
-                torch.arange(d2, dtype=torch.float32),
-                torch.arange(d3, dtype=torch.float32),
-                indexing='ij',
-            )
-            distances = torch.minimum(
-                torch.minimum(mi, mj),
-                torch.minimum(d2 - 1 - mi, d3 - 1 - mj),
-            )
-            # convert distances to square falloff from 1 to 0
-            t = (feathering - distances) / feathering
-            t.clamp_(min=0)
-            t.square_()
-
-            mask[top:top + d2, left:left + d3] = t
-        else:
-            mask[top:top + d2, left:left + d3] = torch.zeros(
-                (d2, d3),
-                dtype=torch.float32,
-            )
+
+            for i in range(d2):
+                for j in range(d3):
+                    dt = i if top != 0 else d2
+                    db = d2 - i if bottom != 0 else d2
+
+                    dl = j if left != 0 else d3
+                    dr = d3 - j if right != 0 else d3
+
+                    d = min(dt, db, dl, dr)
+
+                    if d >= feathering:
+                        continue
+
+                    v = (feathering - d) / feathering
+
+                    t[i, j] = v * v
+
+        mask[top:top + d2, left:left + d3] = t
 
         return (new_image, mask)