[Gllug] Faster maths?

[SteveC]

doesn't image magick `convert` /perlmagick do it?

Adrian McMenamin wrote:
> I have some perl which indexes and dithers a PNG image to a 256 colour
> palette.
> 
> The indexing is pretty fast - a 59K (compressed) PNG image on a 4000
> BogoMIPS machine in about a second.
> 
> But I turn on dithering it takes half an hour!!
> 
> The bottleneck appears to be calculating the distance of a point in
> colourspace (ie the original colour + diffused error) from any point in
> the palette (to find the closest match).
> 
> I don't use sqrt - just compare square with square (and save a match so
> don't have to do the same lookup twice).
> 
> But generally this requires several tens of millions of comparisons for
> a reasonably large image.
> 
> There must be a better way as I know C libraries obviously don't take
> this long (do they?) and the difference in speed is so great it cannot
> simply be perl versus C that is the issue.
> 
> I know this is a bit of a specialist subject - but anybody know of
> faster ways to calculate distances in a three dimensional space and/or
> work out how to compare with a smaller range of numbers than the whole
> 24 bit palette?
> 
> 

-- 
have fun,

SteveC steve at asklater.com http://www.asklater.com/steve/
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