add polygons

ppocr/postprocess/db_postprocess.py

@@ -236,7 +236,7 @@ class DBPostProcess(object):
                     self.dilation_kernel)
             else:
                 mask = segmentation[batch_index]
-            if self.use_polygon:
+            if self.use_polygon is True:
                 boxes, scores = self.polygons_from_bitmap(pred[batch_index],
                                                           mask, src_w, src_h)
             else: