postprocessor.py: fix NumPy array issue when using latest opencv release (#179)

Signed-off-by: Longyin Hu <longyin.hu@intel.com>

Author: Hulongyin

cnap/core/processors/postprocessor.py

@@ -74,6 +74,7 @@ def postprocess(self, frame: np.ndarray, outputs: dict) -> np.ndarray:
         Postprocess the output by drawing boxes and labels on the input frame for
         object detection.
         """
+        frame = frame.copy()
         try:
             if self._drawing.get('draw_boxes'):
                 boxes = outputs['detection_boxes']
@@ -121,6 +122,7 @@ def postprocess(self, frame: np.ndarray, outputs: dict) -> np.ndarray:
         Postprocess the output by drawing boxes and labels on the input frame for
         object detection.
         """
+        frame = frame.copy()
         try:
             if self._drawing.get('draw_landmarks'):
                 facial_landmarks = outputs['facial_landmarks']