[Numpy-discussion] Learn about numpy
Nadav Horesh
nadavh@visionsense....
Sun May 4 05:13:00 CDT 2008
What you do here is a convolution with
0 1 0
1 1 1
0 1 0
kernel, and thresholding, you can use numpy.numarray.nd_image package:
import numpy.numarray.nd_image as NI
.
.
.
ker = array([[0,1,0], [1,1,1],[0,1,0]])
result = (NI.convolve(self.bufbw, ker) == 1).astype(uint8)
for nore general cases you can use the function generic_filter in the same package.
Nadav.
-----הודעה מקורית-----
מאת: numpy-discussion-bounces@scipy.org בשם Folkert Boonstra
נשלח: א 04-מאי-08 12:52
אל: numpy-discussion@scipy.org
נושא: [Numpy-discussion] Learn about numpy
With a python background but new to numpy, I have the following.
Suppose I have a 2-D array and I want to apply a function to each element.
The function needs to access the direct neighbouring elements in order
to set a new value for the element. How would I do that in the most
efficient way with numpy?
Currently I have a uint8 array (self.bufbw) filled with 0 and 1 elements:
def applyRule(self, rule):
for xy in self.xydims:
rule(xy)
def rule(self, xy):
x = xy[0]; y = xy[1]
sum = self.bufbw[x-1:x+2, y-1:y+2].sum() \
- self.bufbw[x-1,y-1] - self.bufbw[x+1,y-1] \
- self.bufbw[x-1,y+1] - self.bufbw[x+1,y+1]
if sum == 1:
self.bufbw[x,y] = 1
else:
self.bufbw[x,y] = 0
I have looked at the documentation online but couldn't find another faster solution yet.
Does anyone want to share some ideas on a faster solution with numpy?
Thanks,
Folkert
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