diff --git a/csst_proto/flip_image.py b/csst_proto/flip_image.py
index 109e7a16339aa0fc78be98ae225b306e2d72f9eb..7f7aa41f2be483f65a80e44bc924549b15df4977 100644
--- a/csst_proto/flip_image.py
+++ b/csst_proto/flip_image.py
@@ -26,10 +26,8 @@ def flip_image(img: np.ndarray):
     return img[::-1, ::-1]
 
 
-# a demo on how to package data
-def print_data():
-    """ print out data """
-    fp_data = PACKAGE_PATH + "/data/data.csv"
-    data = table.Table.read(fp_data)
-    print(data)
-    return
+# a demo on how to read test image
+def read_test_image():
+    """ read test image """
+    fp_img = PACKAGE_PATH + "/data/test_image.txt"
+    return np.loadtxt(fp_img)
diff --git a/csst_proto/top_level_interface.py b/csst_proto/top_level_interface.py
index aa96701c1ea1dacc21279e484059177099d17cec..d5b7afbf84e2dad4c9d747c3779edee41b4328e8 100644
--- a/csst_proto/top_level_interface.py
+++ b/csst_proto/top_level_interface.py
@@ -1,4 +1,4 @@
-from .flip_image import flip_image, print_data
+from .flip_image import flip_image, read_test_image
 
 
-__all__ = ["flip_image", "print_data"]
+__all__ = ["flip_image", "read_test_image"]