[Numpy-discussion] Adjacent matrix
Thiago Franco Moraes
totonixsame@gmail....
Mon Jun 13 14:55:46 CDT 2011
Hi all,
I'm reproducing a algorithm from a paper. This paper takes as input a
binary volumetric matrix. In a step from this paper, from this binary
volumetric matrix a adjacent matrix is calculated, thisadjacent matrix
is calculated as bellow:
"Find all of the grid points in that lie adjacent to one or more grid
points of opposite values."
This is the code used to calculate that matrix:
int x,y,z,x_,y_,z_, addr,addr2;
for(z = 1; z < nz-1; z++)
for(y = 1; y < ny-1; y++)
for(x = 1; x < nx-1; x++)
for(z_=z-1; z_ <= z+1; z_++)
for(y_=y-1; y_ <= y+1; y_++)
for(x_=x-1; x_ <= x+1; x_++)
{
addr = z*nx*ny+y*nx+x;
addr2 = z_*nx*ny+y_*nx+x_;
if(im[addr] != im[addr2])
out[addr] = 1;
}
Where nx, ny and nz are the x, y, z dimensions from the "im" input
binary matrix. I think this operation is called bwperim.
Yes, I can reproduce that code in Python. But it will not have a great
performance. My question is: Is there a way to do that using numpy or
scipy tools?
Thanks!
PS: Those indexing starts with 1 because it is a matlab arrays however
it is coded in C.
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