Fix imshow()ing PIL-opened images.

We actually handle grayscale images just fine, but they need to be
transformed into masked arrays like everyone else.

Author: anntzer

lib/matplotlib/image.py

@@ -649,15 +649,7 @@ def set_data(self, A):
         ----------
         A : array-like
         """
-        # check if data is PIL Image without importing Image
-        if hasattr(A, 'getpixel'):
-            if A.mode == 'L':
-                # greyscale image, but our logic assumes rgba:
-                self._A = pil_to_array(A.convert('RGBA'))
-            else:
-                self._A = pil_to_array(A)
-        else:
-            self._A = cbook.safe_masked_invalid(A, copy=True)
+        self._A = cbook.safe_masked_invalid(A, copy=True)
 
         if (self._A.dtype != np.uint8 and
                 not np.can_cast(self._A.dtype, float, "same_kind")):

lib/matplotlib/tests/test_image.py

@@ -18,7 +18,7 @@
 from matplotlib.cbook import MatplotlibDeprecationWarning
 from matplotlib.image import (AxesImage, BboxImage, FigureImage,
                               NonUniformImage, PcolorImage)
-from matplotlib.testing.decorators import image_comparison
+from matplotlib.testing.decorators import check_figures_equal, image_comparison
 from matplotlib.transforms import Bbox, Affine2D, TransformedBbox
 
 import pytest
@@ -106,6 +106,15 @@ def test_image_python_io():
     plt.imread(buffer)
 
 
+@check_figures_equal()
+def test_imshow_pil(fig_test, fig_ref):
+    pytest.importorskip("PIL")
+    img = plt.imread(os.path.join(os.path.dirname(__file__),
+                     'baseline_images', 'test_image', 'uint16.tif'))
+    fig_test.subplots().imshow(img)
+    fig_ref.subplots().imshow(np.asarray(img))
+
+
 def test_imread_pil_uint16():
     pytest.importorskip("PIL")
     img = plt.imread(os.path.join(os.path.dirname(__file__),