STRIP implementation doesn't match original codebase

[Kshitij Sachan]

Your STRIP defense implementation seems reasonable (linearly mix benign and test inputs), but this is different from the official implementation from the STRIP repo, where they just add both images on top of each other. Not sure if this was intentional or not.

Trojanzoo implementation:

trojanzoo/trojanvision/defenses/backdoor/input_filtering/strip.py

Line 74 in 58d309b

 test_input = self.strip_alpha * (_input - benign_input) + benign_input 

original STRIP implementation:

def superimpose(background, overlay):
  added_image = cv2.addWeighted(background,1,overlay,1,0)
  return (added_image.reshape(32,32,3))

[Ren Pang]

According to opencv documents, I don't see any difference between the 2 implementations.