fix infer not visualize (#2578)

PaddleCV/object_detection/tools/infer.py

@@ -56,6 +56,10 @@ def get_test_images(infer_dir, infer_img):
     """
     assert infer_img is not None or infer_dir is not None, \
         "--infer_img or --infer_dir should be set"
+    assert infer_img is None or os.path.isfile(infer_img), \
+            "{} is not a file".format(infer_img)
+    assert infer_dir is None or os.path.isdir(infer_dir), \
+            "{} is not a directory".format(infer_dir)
     images = []
 
     # infer_img has a higher priority
@@ -162,8 +166,8 @@ def main():
         for im_id in im_ids:
             image_path = imid2path[int(im_id)]
             image = Image.open(image_path).convert('RGB')
-            visualize_results(image, int(im_id), catid2name, 0.5, bbox_results,
-                              mask_results, is_bbox_normalized)
+            image = visualize_results(image, int(im_id), catid2name, 0.5, 
+                        bbox_results, mask_results, is_bbox_normalized)
             save_name = get_save_image_name(FLAGS.output_dir, image_path)
             logger.info("Detection bbox results save in {}".format(save_name))
             image.save(save_name)