matplotlib · mdboom · Jul 17, 2016 · Jul 20, 2016 · Jul 25, 2016 · Oct 17, 2016
diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -22,6 +22,7 @@
 import matplotlib.colors as mcolors
 import matplotlib.cm as cm
 import matplotlib.cbook as cbook
+from matplotlib import patches as mpatches
 
 # For clarity, names from _image are given explicitly in this module:
 import matplotlib._image as _image
@@ -299,6 +300,8 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
         `trans` is the affine transformation from the image to pixel
         space.
         """
+        from matplotlib import axes as maxes
+
         if A is None:
             raise RuntimeError('You must first set the image'
                                ' array or the image attribute')
@@ -336,11 +339,15 @@ def _make_image(self, A, in_bbox, out_bbox, clip_bbox, magnification=1.0,
                  -clipped_bbox.y0)
              .scale(magnification, magnification))
 
-        # So that the image is aligned with the edge of the axes, we want
-        # to round up the output width to the next integer.  This also
-        # means scaling the transform just slightly to account for the
-        # extra subpixel.
-        if (t.is_affine and round_to_pixel_border and
+        # So that the image is aligned with the edge of the axes, we
+        # want to round up the output width to the next integer.  This
+        # also means scaling the transform just slightly to account
+        # for the extra subpixel.  This is only required for regular
+        # rectangular axes where the edges are pixel-snapped.  For
+        # non-rectangular axes, this refinement isn't required.
+        if (round_to_pixel_border and
+            t.is_affine and
+            isinstance(self.axes, mpatches.Rectangle) and
             (out_width_base % 1.0 != 0.0 or
              out_height_base % 1.0 != 0.0)):
             out_width = int(ceil(out_width_base) + 1)

diff --git a/lib/mpl_toolkits/tests/baseline_images/test_axes_grid/imagegrid_cbar_mode.png b/lib/mpl_toolkits/tests/baseline_images/test_axes_grid/imagegrid_cbar_mode.png