Hi all,
I've been using idlanroigroup to create masks and there I've found
something to be aware of. Let's say you have a background mask that
goes from masked (value = 0, "-") to unmasked (value = 255, "+") like
so:
------++++++
------++++++
------++++++
------++++++
------++++++
------++++++
Now you want to do further masking on this, like so (cut out a
semicircle:
------++++++
-------+++++
--------++++
--------++++
-------++++
------++++++
What you will get will be a *filled* semicircle - it will not be
masked out. This applies only when the boundary goes from 0 to 255
from left to right. This sort of boundary: ++++----- does not produce
this problem. It must have something to do with how the mask array is
filled.
Here's an example: http://people.bu.edu/andersld/mask.jpg
-Loren
