Merge pull request #18504 from meeseeksmachine/auto-backport-of-pr-18500-on-v3.3.x

QuLogic · web-flow · commit e2dd1ba87d73 · 2020-09-17T02:21:27.000-04:00
Backport PR #18500 on branch v3.3.x (BUG: Fix all-masked imshow)
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -474,8 +474,10 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
                 # do not run the vmin/vmax through the same pipeline we can
                 # have values close or equal to the boundaries end up on the
                 # wrong side.
-                vrange = np.array([self.norm.vmin, self.norm.vmax],
-                                  dtype=scaled_dtype)
+                vmin, vmax = self.norm.vmin, self.norm.vmax
+                if vmin is np.ma.masked:
+                    vmin, vmax = a_min, a_max
+                vrange = np.array([vmin, vmax], dtype=scaled_dtype)
 
                 A_scaled -= a_min
                 vrange -= a_min
diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -846,6 +846,14 @@ def test_mask_image():
     ax2.imshow(A, interpolation='nearest')
 
 
+def test_mask_image_all():
+    # Test behavior with an image that is entirely masked does not warn
+    data = np.full((2, 2), np.nan)
+    fig, ax = plt.subplots()
+    ax.imshow(data)
+    fig.canvas.draw_idle()  # would emit a warning
+
+
 @image_comparison(['imshow_endianess.png'], remove_text=True)
 def test_imshow_endianess():
     x = np.arange(10)
