Hi Ben
Yes, in mathematica it takes approximately 2 minutes to do the 13x13
medianfilter for a 2004 x 2006 picture... I usually use much bigger
boxsizes (about 120x120), so I can pick up a coffee while the program is
running.
What you write about your use of J sounds promising to me. I ordered the
book from Reiter in the library and will have a look at it. The
tutorials you mentioned: are they somehow available?
Thanks a lot for your answers!
On 04/24/2013 04:14 PM, Ben Gorte - CITG wrote:
By the way, Cliff Reiter's median in J isn't slow at all, for example compared
to famous software like ImageMagick:
$ time convert -median 3x3 p19.pgm m3.pgm
real 0m11.961s
user 0m22.333s
sys 0m0.292s
$
$ time convert -median 13x13 p19.pgm m13.pgm
real 1m13.204s
user 2m22.517s
sys 0m0.352s
Good old xv uses 10s resp. 5 minutes.
Ben
________________________________________
From: [email protected] [[email protected]] on
behalf of Ben Gorte - CITG [[email protected]]
Sent: Wednesday, April 24, 2013 15:47
To: [email protected]
Subject: Re: [Jchat] J for Image Processing
6!:2 'med3 =: 3 medianf p19'
17.9526
6!:2 'med13 =: 13 medianf p19'
47.2474
$p19
3072 4608
(A median 3x3 median filter on a 3072x4608 image takes 18s, and a 13x13 median
takes 47s).
This is on an Intel Core 2 Duo CPU at 2.00GHz , using the median function from the
already-mentioned book of Cliff Reiter "Fractals, Visualization and J":
medianf =: 1 : '(2#m) "_ (<.-:*:m)&{@:(/:~)@,;._3 ]'
I have a C program doing the same in 0.7s resp. 1.2s, but when I consider how
much time it took me to write that one, I must compute an awful lot of medians
with it before earning back that time.
Ben
________________________________________
From: [email protected] [[email protected]] on
behalf of Sarah Arnold [[email protected]]
Sent: Wednesday, April 24, 2013 15:02
To: [email protected]
Subject: Re: [Jchat] J for Image Processing
Hi
I should have been a bit more precise: I'm into astronomy. I'm mostly
interested in noise reduction / signal enhancement and therefore apply
different filters to the image. Some of this operations, like for
example the MedianFilter[] function, take a lot of computation time.
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