docs for calculate percentage difference

CAM2ImageArchiver/CameraHandler.py

@@ -98,6 +98,10 @@ def run(self):
                                 frame_timestamp).strftime('%Y-%m-%d_%H-%M-%S-%f'))
 
                         if self.image_difference_percentage:
+                            # Check the percentage difference if last frame is not None
+                            # by calculating the pixel-by-pixel value difference between
+                            # last frame and current frame, then divide the diff by frame size.
+                            # Count pixel value by using numpy. Check numpy docs for np.absolute and np.count_nonzero
                             if frame.size != 0 and (type(camera.last_frame) == type(None) or (np.count_nonzero(np.absolute(camera.last_frame - frame)) * 100) / frame.size >= self.image_difference_percentage):
                                 cv2.imwrite(file_name, frame)
                                 camera.last_frame = frame

CAM2ImageArchiver/test/test_camera.py

@@ -23,7 +23,6 @@
 from CAM2ImageArchiver.CAM2ImageArchiver import CAM2ImageArchiver
 sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
-
 class TestCamera(unittest.TestCase):
 
     def setUp(self):
@@ -39,7 +38,7 @@ def setUp(self):
             'camera_type': 'ip',
             'ip': '207.251.86.238',
             'port': '',
-            'image_path': '/cctv254.jpg',
+            'image_path': '/cctv290.jpg',
             'video_path': '/axis-cgi/mjpg/video.cgi'
         }
         cam3 = {