perf: faster 26-connected connected_components_stack

Author: william-silversmith

cc3d/__init__.py

@@ -447,6 +447,14 @@ def connected_components_stack(
           if bottom_cc_labels[x,y] == 0:
             continue
 
+          if ((not binary_image and bottom_cc_img[x,y] == image[x,y,0])
+                or (binary_image and bottom_cc_img[x,y] and image[x,y,0])):
+
+            equivalences.union(
+              bottom_cc_labels[x,y], top_cc_labels[x,y]
+            )
+            continue
+
           for y0 in range(max(y - 1, 0), min(y + 1, image.shape[1] - 1) + 1):
             for x0 in range(max(x - 1, 0), min(x + 1, image.shape[0] - 1) + 1):
               if top_cc_labels[x0,y0] == 0: