Example 10a: Using high-resolution background maps during
zooming with fixed zoom factors
This is like the previous example, except that we want to
zoom only to the resolutions of the two "hi_res" images.
The configuration file has been changed to specify that the
"zoom_scale" must use the "hi_res_zoom" values from the
file_of_filenames = fof10.txt
zoom_scale = hi_res
So, for each 'click', the next hi_res map is shown..whether you
zoom in or out.