move the shuffer into def sample_iter_reader

ppocr/data/det/dataset_traversal.py

@@ -41,13 +41,12 @@ class TrainReader(object):
             label_infor_list = fin.readlines()
         img_num = len(label_infor_list)
         img_id_list = list(range(img_num))
-        if sys.platform == "win32":
-            random.shuffle(img_id_list)
+        if sys.platform == "win32" and self.num_workers != 1:
             print("multiprocess is not fully compatible with Windows."
                   "num_workers will be 1.")
             self.num_workers = 1
-                
         def sample_iter_reader():
+            random.shuffle(img_id_list)
             for img_id in range(process_id, img_num, self.num_workers):
                 label_infor = label_infor_list[img_id_list[img_id]]
                 outs = self.process(label_infor)