update inversion code

app.py

@@ -16,8 +16,9 @@ def detect_edges(image:str, sigma, upper_thresh, lower_thresh)->np.ndarray:
         low_threshold=lower_thresh,
         high_threshold=upper_thresh,
     )
-    inverted_image = cv2.bitwise_not(edges)
-    return inverted_image*255
+    edges = edges*255
+    inverted_image_array = 255 - edges
+    return inverted_image_array
 
 edge_detector_interface = gr.Interface(
     fn=detect_edges,