Warn via logging, add test

Zac-HD · Zac-HD · commit 5059e7ec1c95 · 2018-01-12T00:31:45.000+11:00
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -13,7 +13,7 @@
 
 from math import ceil
 import os
-import warnings
+import logging
 
 import numpy as np
 
@@ -35,6 +35,8 @@
 from matplotlib.transforms import (Affine2D, BboxBase, Bbox, BboxTransform,
                                    IdentityTransform, TransformedBbox)
 
+_log = logging.getLogger(__name__)
+
 # map interpolation strings to module constants
 _interpd_ = {
     'none': _image.NEAREST,  # fall back to nearest when not supported
@@ -618,7 +620,7 @@ def set_data(self, A):
             # making reliable interpretation impossible.
             high = 255 if np.issubdtype(self._A.dtype, np.integer) else 1
             if self._A.min() < 0 or high < self._A.max():
-                warnings.warn(
+                _log.warn(
                     'Clipping input data to the valid range for imshow with '
                     'RGB data ([0..1] for floats or [0..255] for integers).'
                 )
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -602,7 +602,7 @@ def test_minimized_rasterized():
 def test_load_from_url():
     req = six.moves.urllib.request.urlopen(
         "http://matplotlib.org/_static/logo_sidebar_horiz.png")
-    Z = plt.imread(req)
+    plt.imread(req)
 
 
 @image_comparison(baseline_images=['log_scale_image'],
@@ -795,6 +795,17 @@ def test_imshow_no_warn_invalid():
     assert len(warns) == 0
 
 
+@pytest.mark.parametrize('as_float', [True, False])
+def test_imshow_logs_when_clipping_invalid_rgb(as_float, caplog):
+    arr = np.arange(300).reshape((10, 10, 3))
+    if as_float:
+        arr = arr / 255
+    fig = plt.figure()
+    ax = fig.add_subplot(111)
+    ax.imshow(arr)
+    assert 'Clipping input data to the valid range for imshow' in caplog.text
+
+
 @image_comparison(baseline_images=['imshow_flatfield'],
                   remove_text=True, style='mpl20',
                   extensions=['png'])
