Merge pull request #2552 from WenmuZhou/2.1_require

update requirements

requirements.txt

@@ -3,8 +3,8 @@ scikit-image==0.17.2
 imgaug==0.4.0
 pyclipper
 lmdb
-opencv-python==4.2.0.32
 tqdm
 numpy
 visualdl
-python-Levenshtein
\ No newline at end of file
+python-Levenshtein
+opencv-contrib-python==4.2.0.32
\ No newline at end of file