On Apr 9, 12:05 pm, "R.G. Stockwell" <noem...@please.com> wrote:
> I need to cut an image into 4 equal-size parts, which
> obviously is very easy to do in a few lines.
> image1 = im[0:nx/2-1, 0:ny/2-1]
> image2 = im[0:nx/2-1, ny/2:*]
> image3 = im[nx/2:*, 0:ny/2-1]
> image4 = im[nx/2:*, ny/2:*]
>
> i came across a way to do this with reform, but
> it required 4 steps ( several reforms, a couple transposes)
> to do it properly.
>
> I'd be interested (just for fun) in a vectorized general way to do this
> if any of you 'dimension jugglers' have any clever ideas,
> for how to take an image and cut it into 4, or 16, or 64,
> or 256 equal pieces (that would probably be about the maximum)
Well, if it is just for fun, why not use a recursive approach?
I always like the simplicity of these :) (though they are not
always the most efficient way, and sometimes they are the worst
way to do it).
res=segim(dist(512,512),level=4)
IDL> help,res
RES FLOAT = Array[8192, 32]
The output is just an array with the images side by side, i.e.
[im1,im2,...,im256].
There are (2^level)^2 subarrays. That is,
lev =1 -> 4
lev =2 -> 16
lev =3 -> 64
lev =4 -> 256
etc.
Ciao,
Paolo
FUNCTION segim,im,level=level
IF n_elements(level) EQ 0 THEN level=4
n=size(im,/dimension)
nx=n[0]
ny=n[1]
IF level EQ 0 THEN return,im
return,[segim(im[0:nx/2-1, 0:ny/2-1],level=level-1),segim(im[0:nx/2-1,
ny/2:*],level=level-1), $
segim(im[nx/2:* , 0:ny/2-1],level=level-1),segim(im[nx/2:* ,
ny/2:*],level=level-1)]
END
>
> cheers,
> bob
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