Hi, all. There have been some discussions about using axes_grid1.AxisDivider with polar projected images to make axis for a colorbar with proper height/width (E.g., my comment on an old issue #3286 and ). It appears to me that there is a bug in axes_grid1.axes_size.AxisX and AxisY that assume rectangular projection.

I changed mpl_toolkits.axes_grid1.axes_size.py a little to support polar projection (almost) properly. Please see https://gist.github.com/jimgreen/839f43897e9c1d54f6fb4b890a93ee1b for a working example.
The result after fixing is of the left, and the simple call to plt.colorbar() is on the right:

I wonder if this the right thing to do? And, perhaps we need to support other projections, too?

PS:

• I also forced to use axes_class=matplotlib.axes._axes.Axes in divider.append_axes to get the proper axis for colorbar. Otherwise the returned ax would have same projection as the input ax, which is polar.
• The often suggested solution of using GridSpec is also nice (see https://stackoverflow.com/questions/24894625/adding-a-colorbar-to-a-pcolormesh-with-polar-projection). But it (to me) is a very different solution to the axes_grid1 way.