Hi Tim,
In general, this isn't easily threadable, as there are a different number
of pixels to be medianed in each ring. It's possible, but I think you're
okay with using a loop because at least the code is readable and you'll
wonder what on earth you were doing if you try to reread it several months
later.
My only other comment is that you're only selecting *exactly* the same
values for the radius of the ring, which is a bit too restrictive.
Here's my go at that:
my $image = grandom(zeroes(101,101));
my $dr = 3;
for (my $r = 0; $r < 50; $r += $dr) {
$image = medring($image, 20, 30, $r, $r+$dr);
}
sub medring {
# replace the annulus centered at x,y between radii r1 and r2
# with the median value of that ring
# CAUTION: it modifies $im in place! Make a copy if you don't want
# to modify the original im
use strict;
my ($im, $x, $y, $r1, $r2) = @_;
my $rv = rvals($im, {CENTER=>[$x,$y]} ) ;
my $ringmask = ($rv >= $r1) * ($rv < $r2);
my $ring = $im->where($ringmask);
my $medring = median ($ring);
$ring .= $medring;
return($im);
}
On Thu, Jan 3, 2013 at 4:30 AM, Karl Glazebrook <[email protected]>wrote:
> Or rvals()
>
>
> On 25/12/2012, at 1:31 PM, Tim Haines wrote:
>
> > Hello, all.
> >
> > I am currently working with some simple 2D data, and I would like to
> replace all of the pixel values lying along the same circular annulus with
> their median. Currently, I am doing the following:
> >
> > my $image = rfits('input.fits');
> > my $radii = $image->long->inplace->rvals;
> >
> > for my $radius ($radii->uniq->list)
> > {
> > $image->whereND($radii==$radius) .=
> $image->whereND($radii==$radius)->clump(-1)->medover;
> > }
> >
> >
> > I would like to get rid of the perl loop. I have tried using higher
> dimensions in the whereND mask, but I couldn't quite get the threading to
> work out for my purposes.
> >
> > Any thoughts?
> >
> > Many thanks.
> >
> > - Tim
> > _______________________________________________
> > Perldl mailing list
> > [email protected]
> > http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
>
>
> _______________________________________________
> Perldl mailing list
> [email protected]
> http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
>
>
--
Matthew Kenworthy / Assistant Professor / Leiden Observatory
Niels Bohrweg 2 (#463) / P.O. Box 9513 / 2300 RA Leiden / NL
_______________________________________________
Perldl mailing list
[email protected]
http://mailman.jach.hawaii.edu/mailman/listinfo/perldl
