fix big input size of shrink (#4090)

PaddleCV/face_detection/widerface_eval.py

@@ -22,11 +22,13 @@ import argparse
 import functools
 from PIL import Image
 
+
 def set_paddle_flags(**kwargs):
     for key, value in kwargs.items():
         if os.environ.get(key, None) is None:
             os.environ[key] = str(value)
 
+
 # NOTE(paddle-dev): All of these flags should be
 # set before `import paddle`. Otherwise, it would
 # not take any effect.
@@ -34,7 +36,6 @@ set_paddle_flags(
     FLAGS_eager_delete_tensor_gb=0,  # enable GC to save memory
 )
 
-
 import paddle.fluid as fluid
 import reader
 from pyramidbox import PyramidBox
@@ -315,6 +316,8 @@ def get_shrink(height, width):
         max_shrink = max_shrink - 0.4
     elif max_shrink >= 5:
         max_shrink = max_shrink - 0.5
+    elif max_shrink <= 0.1:
+        max_shrink = 0.1
 
     shrink = max_shrink if max_shrink < 1 else 1
     return shrink, max_shrink