[Numpy-discussion] Learn about numpy

Folkert Boonstra F.Boonstra@inter.nl....
Tue May 6 04:36:15 CDT 2008

Nadav Horesh schreef:
> I think you have a problem of overflow in r5: You may better use utin64 instead of uint32.
>   Nadav.

My problems were due to trying to do two things at once.
The code below does what I want and it is very fast. I see the power of
numpy now:

import numpy as NU
import numpy.numarray.nd_image as NI

BW = NU.zeros((5,5), dtype=NU.uint8)
AR = NU.zeros((5,5), dtype=NU.uint32)
DA = NU.zeros((5,5), dtype=NU.uint32)
LA = NU.zeros((5,5), dtype=NU.uint32)

DC = 4278190280
LC = 4278241280

BW[1,1] = 1
BW[2,2] = 1
AR[:] = DC
AR[1,1] = LC
AR[2,2] = LC
DA[:] = DC
LA[:] = LC

kernel = NU.array([[0,1,0], \
                   [1,1,1], \

print "AR=\n", AR

r1 = NI.convolve(BW, kernel).astype(NU.uint8)
r2 = (NI.convolve(BW, kernel) == 1).astype(NU.uint8)
print "r1=\n",r1
print "r2=\n",r2

# create 32-bit array using results from convolve as mask
AR = NU.array(DA, copy=1)
NU.putmask(AR, r2, LA)

print "AR=\n", AR

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