Update app.py

app.py

@@ -61,9 +61,10 @@ def blend_images(base, overlay, mask):
         mask = mask.astype(np.uint8) * 255
 
     # Ensure mask is single-channel grayscale
-    if len(mask.shape) == 3:
+    # Ensure mask is single-channel grayscale
+    if len(mask.shape) == 3 and mask.shape[2] == 3:
         mask = cv2.cvtColor(mask, cv2.COLOR_BGR2GRAY)
-
+    
     # Convert mask to uint8 if necessary
     if mask.dtype != np.uint8:
         mask = (mask * 255).astype(np.uint8)