Re[2]:[9fans] image resampling

Re[2]:[9fans] image resampling

[steve.simon]

Re OS-X, The simple answer is, no idea.

They maybe using hardware acceleration of the graphics device?

Maybe OS-X is not resampling a full 24 bit RGB image as the plan9 one is?

There is a  trick you can do throwing memory at the problem,  if your image is 8
bits
deep and you have 8 coefficients then you have 64K  entry
lookup table instead of a multiplier. I haven't tried this for
years - it was a win in the days of slow multiply instructions, probably
irrelevant now.

The vertical pass can cause rather nasty RAM access patterns and may
upset the CPU's data cache, Rotating the array by 90 degrees and reapplying the
same horizontal filter code (though not the coefficients -
non-square aspect ratios) might help.

All a bit speculative though, Russ's code looks a very sane implementation to
me.

-Steve



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Re: [9fans] image resampling

[Boyd Roberts]

steve.simon@snellwilcox.com wrote:
>
> Re OS-X, The simple answer is, no idea.

Geoff Collyer may be able to answer that one.

[9fans] image resampling

[++pac]

Hi, friends,

can anyone advise me how to resample (scale down) a big bitmap image?
I browsed through iconv(1), crop(1), jpg(1) ... still having no idea.
Just wanna look at my pictures without going to linux 'convert' :-((

TIA,
++pac.