Optimizing numpy

[Gerdus van Zyl]

I have the following, that is used to convert pixel data and thus
should be as fast as possible:

b = numpy.ndarray (shape=(w,h,4), dtype=numpy.uint8)

a = numpy.frombuffer(buf, numpy.uint8)
a.shape = (w, h, 3)

b[:,:,0] = a[:,:,2]
b[:,:,1] = a[:,:,1]
b[:,:,2] = a[:,:,0]
b[:,:,3] = 255

Can anyone tell me if there is a faster way? Will making use of
weave.blitz or pyrex help?

Thank You.