fix small bug on jpeg_compression

Author: minhitbk

art/defences/jpeg_compression.py

@@ -31,7 +31,7 @@ def __init__(self, quality=50, channel_index=3):
         self._is_fitted = True
         self.set_params(quality=quality, channel_index=channel_index)
 
-    def __call__(self, x, y=None, quality=None):
+    def __call__(self, x, y=None, quality=None, clip_values=(0, 1)):
         """
         Apply jpeg compression to sample `x`.
 
@@ -92,6 +92,8 @@ def __call__(self, x, y=None, quality=None):
         if self.channel_index < 3:
             x_ = np.swapaxes(x_, self.channel_index, 3)
 
+        x_ = np.clip(x_, clip_values[0], clip_values[1])
+
         return x_
 
     def fit(self, x, y=None, **kwargs):