Add check before int casting for PIL conversion (#21969)

* Add check before int casting for PIL conversion

* Line length

* Tidier logic

tests/test_image_transforms.py

@@ -96,6 +96,11 @@ class ImageTransformsTester(unittest.TestCase):
         # make sure image is correctly rescaled
         self.assertTrue(np.abs(np.asarray(pil_image)).sum() > 0)
 
+        # Make sure that an exception is raised if image is not in [0, 1]
+        image = np.random.randn(*image_shape).astype(dtype)
+        with self.assertRaises(ValueError):
+            to_pil_image(image)
+
     @require_tf
     def test_to_pil_image_from_tensorflow(self):
         # channels_first