Update utils.py (#1508)

The binary mode of fromstring is deprecated, as it behaves surprisingly on unicode inputs. Use frombuffer instead

modules/image/text_recognition/chinese_ocr_db_crnn_server/utils.py

@@ -172,6 +172,6 @@ def sorted_boxes(dt_boxes):
 
 def base64_to_cv2(b64str):
     data = base64.b64decode(b64str.encode('utf8'))
-    data = np.fromstring(data, np.uint8)
+    data = np.frombuffer(data, np.uint8)
     data = cv2.imdecode(data, cv2.IMREAD_COLOR)
     return data