[gdal-dev] Converting palette image to RBG

[Frank Warmerdam]

Christopher Barker wrote:
> As I'm doing this on the fly, I'd like it to be fast -- the pct2rgb.py 
> code uses numpy, but it looks like it's processing the image line by 
> line, and also looping through the color table. I need to do more 
> testing to see if this is really too slow, but it would be nice to have 
> all that looping in C -- and I can't be the only one that would use such 
> functionality.

Chris,

The Numeric.take() directive should be a fast way to do lookups, and
one whole scanline at a time is handled rather than looping over the
pixels. So I think that pct2rgb.py is pretty fast.

Of course, it is also easy to replicate the capability in C.

> Another thought -- my workflow may be a bad idea anyway -- should I 
> convert to RBG first, and then re-scale it? You must not be able to 
> interpolate smoothly with a palleted image..

If  you want any resampling kernel other than nearest neighbour you
would need to convert to RGB before resampling.

Best regards,
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