[SciPy-user] stupid array tricks
Fri Feb 6 16:08:01 CST 2009
I know there are a number of array manipulation maestros on the list and
wanted to run a problem by the list that my feeble mind is foundering on.
I have three objects, 1) an array containing an "image" (could be any
dimension), 2) a mask for the image (of the same dimensions as the
image), and 3) a "template" which is just a list of offset coordinates
from any point in the image.
Say the template has n elements, the problem is to move the template
over the image and build an m x n array containing image values (at the
template positions) where m is the number of image indices such that the
template lies within the image and all mask values are true. I currently
do this using some raveling, compressing, and length comparison but I
still haven't been able to figure out how to do it without looping
through the image indices (and this is sloooowwww for big
multidimensional "images"). I keep feeling like there must be some
clever way to concatenate the template with the image and mask so as to
do this without looping but haven't been able to come up with it. I
could speed it up by doing the looping in C but that doesn't seem very
elegant. Any thoughts welcome.
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