[Numpy-discussion] fast grayscale conversion

[Alex Flint]

At the moment I'm using numpy.dot to convert a WxHx3 RGB image to a
grayscale image:

src_mono = np.dot(src_rgb.astype(np.float), np.ones(3)/3.);

This seems quite slow though (several seconds for a 3 megapixel image) - is
there a more specialized routine better suited to this?

Cheers,
Alex
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