From 4ca1f49d2002656a1ab8e6b8fe41cce8c90aa306 Mon Sep 17 00:00:00 2001
From: Connelly Barnes <connellybarnes@gmail.com>
Date: Sun, 30 Aug 2015 11:51:04 -0400
Subject: [PATCH 1/2] fix scikit-image bug #1680 (grayscale png round trip
 fails) and add unit test

---
 skimage/io/_plugins/pil_plugin.py | 3 +++
 skimage/io/tests/test_pil.py      | 9 ++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/skimage/io/_plugins/pil_plugin.py b/skimage/io/_plugins/pil_plugin.py
index bb013b0b..4028f3e1 100644
--- a/skimage/io/_plugins/pil_plugin.py
+++ b/skimage/io/_plugins/pil_plugin.py
@@ -87,6 +87,9 @@ def pil_to_ndarray(im, dtype=None, img_num=None):
             i += 1
             continue
 
+        if im.format == 'PNG' and im.mode == 'I' and dtype is None:
+            dtype = 'uint16'
+
         if im.mode == 'P':
             if grayscale is None:
                 grayscale = _palette_is_grayscale(im)
diff --git a/skimage/io/tests/test_pil.py b/skimage/io/tests/test_pil.py
index 935dc6a7..3d0bfe54 100644
--- a/skimage/io/tests/test_pil.py
+++ b/skimage/io/tests/test_pil.py
@@ -6,7 +6,7 @@ from numpy.testing import (
 
 from tempfile import NamedTemporaryFile
 
-from ... import data_dir
+from ... import data_dir, img_as_float
 from .. import imread, imsave, use_plugin, reset_plugins
 from ..._shared.testing import mono_check, color_check
 from ..._shared._warnings import expected_warnings
@@ -39,6 +39,13 @@ def setup_module(self):
     except ImportError:
         pass
 
+def test_png_round_trip():
+    f = NamedTemporaryFile(suffix='.png')
+    fname = f.name
+    I = np.eye(3)
+    imsave(fname, I)
+    Ip = img_as_float(imread(fname))
+    assert np.sum(np.abs(Ip-I)) < 1e-3
 
 def test_imread_flatten():
     # a color image is flattened

From 28a4fcd37e993c90594c565f630731a1bf0bc4f4 Mon Sep 17 00:00:00 2001
From: Connelly Barnes <connellybarnes@gmail.com>
Date: Sun, 30 Aug 2015 21:20:28 -0400
Subject: [PATCH 2/2] fix permissions issue in test_pil.py function
 test_png_round_trip()

---
 skimage/io/tests/test_pil.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/skimage/io/tests/test_pil.py b/skimage/io/tests/test_pil.py
index 3d0bfe54..3a53d340 100644
--- a/skimage/io/tests/test_pil.py
+++ b/skimage/io/tests/test_pil.py
@@ -42,9 +42,11 @@ def setup_module(self):
 def test_png_round_trip():
     f = NamedTemporaryFile(suffix='.png')
     fname = f.name
+    f.close()
     I = np.eye(3)
     imsave(fname, I)
     Ip = img_as_float(imread(fname))
+    os.remove(fname)
     assert np.sum(np.abs(Ip-I)) < 1e-3
 
 def test_imread_flatten():