Hello everybody,
I'm new to python and numpy and have a little/special problem:
I have an numpy array which is in fact a gray scale image mask, e.g.:
mask =
array([[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 255, 255, 255, 0, 0, 255, 0],
[ 0, 0, 255, 255, 255, 0, 0, 255, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0],
[ 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
and I have another array of (y, x) positions in that mask (first two
values of each row):
pos =
array([[ 3., 2., 0., 0.],
[ 3., 4., 0., 0.],
[ 5., 2., 0., 0.],
[ 5., 4., 0., 0.],
[ 6., 2., 0., 0.],
[ 6., 7., 0., 0.],
[ 0., 0., 0., 0.],
[ 8., 8., 0., 0.]])
and now I only want to keep all lines from 2nd array pos with those
indices that are nonzero in the mask, i.e. line 3-6 (pos[2]-pos[5]).
F.e. line 4 in pos has the values (5, 4) and mask[5][4] is nonzero, so I
want to keep it. While line 2 (pos[1]) has the values (4, 6) and
mask[4][6] is zero, so shall be discarded.
I want to avoid a for loop (if possible!!!) cause I think (but don't
know) numpy array are handled in another way. I think numpy.delete is
the right function for discarding the values, but I don't know how to
build the indices.
Maybe someone can help me with that or suggest which way to do this
Sebastian
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