[Numpy-discussion] efficient 3d histogram creation
Sun May 3 19:15:55 CDT 2009
in my endless pursuit of perfomance, i'm searching for a quick way to create
a 3d histogram from a 3d rgb image.
Here is what I have so far for a (16,16,16) 3d histogram:
histarray = N.zeros((16, 16, 16))
temp = imgarray.copy()
(i, j) = imgarray.shape[0:2]
temp = (temp - temp % 16) / 16
for a in range(i):
for b in range(j):
(b1, b2, b3) = temp[a, b, :]
histarray[b1, b2, b3] += 1
this works, but takes about 4 seconds for a 640x480 image.
I tried doing the inverse of my previous post, namely replacing the nested
for loop with:
histarray[temp[:,:,0], temp[:,:,1], temp[:,:,2]] += 1
but that doesn't work for whatever reason. It gives me number, but they're
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Numpy-discussion