imshow feature?

in the example directory the produces a plot that has space between the color plot and the axes on the right side and the bottom.
This occurs if I use the PS or Agg backend. It is evident in the example plot in the 'Screenshots' examples:

The checkerboard goes to the edges but the color overlay has a gap on the right and bottom.
I have not been able to figure this out.

Thanks for any enlightenment.