refactor(preprocessor): add gif chunk prep

gnes/preprocessor/image/segmentation.py

@@ -81,13 +81,14 @@ def apply(self, doc: 'gnes_pb2.Document'):
         else:
             self.logger.error('bad document: "raw_bytes" is empty!')
 
-    def _crop(self, original_image, coordinates):
-        return np.array(original_image.crop(coordinates))
-
     def _get_seg_offset_nd(self, all_subareas: List[List[int]], index: List[List[int]], chunk: List[int]) -> List[int]:
         iou_list = [self._cal_iou(area, chunk) for area in all_subareas]
         return index[int(np.argmax(iou_list))][:2]
 
+    @staticmethod
+    def _crop(original_image, coordinates):
+        return np.array(original_image.crop(coordinates))
+
     @staticmethod
     def _cal_area(coordinate: List[int]):
         return (coordinate[2] - coordinate[0]) * (coordinate[3] - coordinate[1])