In fact, there's no need to get float buffer at all,
conversion could be done in pixel processor level
after interpolation.
It might give slightly worse interpolation results
(which i'm not sure would be visible by eye) but
it gives more than 2x speedup on my laptop on node
setups used for warping image.
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svn merge -r58988:58989 ^/branches/soc-2011-tomato
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