FIX: handle non-native endian images

In cbook.safe_mask_invalid also ensure that the data is in
native byte order.

close matplotlib#6671 closes matplotlib#6394

lib/matplotlib/cbook.py

@@ -1505,6 +1505,13 @@ def issubclass_safe(x, klass):
 
 def safe_masked_invalid(x, copy=False):
     x = np.array(x, subok=True, copy=copy)
+    if not x.dtype.isnative:
+        # Note that the argument to `byteswap` is 'inplace',
+        # thus if we have already made a copy, do the byteswap in
+        # place, else make a copy with the byte order swapped.
+        # Be explicit that we are swapping the byte order of the dtype
+        x = x.byteswap(copy).newbyteorder(new_order='S')
+
     try:
         xm = np.ma.masked_invalid(x, copy=False)
         xm.shrink_mask()

lib/matplotlib/tests/test_image.py

@@ -677,6 +677,21 @@ def test_mask_image():
     ax2.imshow(A, interpolation='nearest')
 
 
-if __name__=='__main__':
-    import nose
-    nose.runmodule(argv=['-s','--with-doctest'], exit=False)
+@image_comparison(baseline_images=['imshow_endianess'],
+                  remove_text=True, extensions=['png'])
+def test_imshow_endianess():
+    x = np.arange(10)
+    X, Y = np.meshgrid(x, x)
+    Z = ((X-5)**2 + (Y-5)**2)**0.5
+
+    fig, (ax1, ax2) = plt.subplots(1, 2)
+
+    kwargs = dict(origin="lower", interpolation='nearest',
+                  cmap='viridis')
+
+    ax1.imshow(Z.astype('<f8'), **kwargs),
+    ax2.imshow(Z.astype('>f8'), **kwargs),
+
+
+if __name__ == '__main__':
+    nose.runmodule(argv=['-s', '--with-doctest'], exit=False)