Merge pull request #101 from stefanv/pil_bilevel_png

BUG: Correctly load bi-level images via PIL.

skimage/io/_plugins/pil_plugin.py

@@ -21,8 +21,9 @@ def imread(fname, dtype=None):
             im = im.convert('L')
         else:
             im = im.convert('RGB')
-
-    if im.mode.startswith('I;16'):
+    elif im.mode == '1':
+        im = im.convert('L')
+    elif im.mode == 'I;16':
         shape = im.size
         dtype = '>u2' if im.mode.endswith('B') else '<u2'
         im = np.fromstring(im.tostring(), dtype)

skimage/io/tests/test_pil.py

@@ -43,6 +43,14 @@ def test_palette_is_gray():
     color = Image.open(os.path.join(data_dir, 'palette_color.png'))
     assert not _palette_is_grayscale(color)
 
+@skipif(not PIL_available)
+def test_bilevel():
+    expected = np.zeros((10, 10))
+    expected[::2] = 255
+
+    img = imread(os.path.join(data_dir, 'checker_bilevel.png'))
+    assert_array_equal(img, expected)
+
 class TestSave:
     def roundtrip(self, dtype, x, scaling=1):
         f = NamedTemporaryFile(suffix='.png')