Since the lena.jpg image needed to be replaced due to bug #794855 I
fetched the replacement that was used by as a replacement in
mathplotlib.  It is available at

   https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/mpl-data/sample_data/grace_hopper.jpg

Since in mgltools-vision a quadratic image is used it was cut to 512x512
first.  Then

   convert grace_hopper_512x512.jpg -geometry 128x128 lena.jpg

was executed to get the final lena.jpg replacement.
