> I encounter problems with the solution below. My test case
> from yesterday was really not a 'test case' because both
> images had near identical values. Thus, the auto vmin,vmax
> settings were the same in both images.
> I think the difference we are seeing may due to the fact
> that the norm attributes are not set until the figure is
> drawn. So in a script with interactive off, the vmin and
> vmax attrs are not updated from None to their True values.
> You can fix this either by working in interactive mode or by
> forcing a draw
Here is a more elegant solution: you don't need to force a draw, you
just need to force an autoscale (which draw does)
from pylab import imshow, rand, show
im = imshow(rand(10,10))
print im.norm.vmin, im.norm.vmax
Now you can pass the vmin and vmax attrs to your new image and expect
them to work. FYI, in your case before when you were passing None,
imshow interprets None to mean "autoscale".