On May 12, 10:52 pm, Gerdus van Zyl <[EMAIL PROTECTED]> wrote:
> 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
You can express this as:
b[:,:,0:3] = a[:,:,2:-1:-1]
b[:,:,3] = 255
> Can anyone tell me if there is a faster way? Will making use of
> weave.blitz or pyrex help?
If you are going to use wave, then don't bother with weave.blitz use
wave.inline instead. You'll need something like this:
code = """
register char a0, a1, a2;
for (int i=0; i<w*h; i++) {
a0 = *a++;
a1 = *a++;
a2 = *a++;
*b++ = a2;
*b++ = a1;
*b++ = a0;
*b++ = 0xFF;
}
"""
wave.inline(code,['a','b','h','w'],compiler='gcc')
Sturla Molden
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