Hey David
Thanks a lot for your code. Edge detection comes pretty close to what I
need. I'm glad to have an example gaussian matrix now.
On 04/24/2013 02:38 PM, David Ward Lambert wrote:
I started to implement the Canny edge detector for rosettacode.org.
http://rosettacode.org/wiki/Canny_edge_detector
The j sentences to create filtering matrices and to then convolve them
with the image them with images is direct with ;. (cut). This is j701
code. After any step step you can look at current result using
viewmat THE_ARRAY
require'bmp viewmat'
NB. use your own path...
TOUCAN=: readbmp'/usr/local/j64-701/addons/graphics/bmp/toucan.bmp'
IMAGE =: TOUCAN
rSquared =: [: +/&.:*:/~ i:
gaussianMatrix =: ^@:((% _2 * *:)~ rSquared) NB. SIGMA gaussianMatrix R
normalize =: % +/@:,
ngm =: normalize@:gaussianMatrix
assert ( 9 11 9 , 11 19 11 ,: 9 11 9 ) -: (<. 0.5 + 100 * 1 ngm 1)
assert (1 1 $ 1) -: 1 ngm 0
FilterArray =: adverb def '(1 1,:$m) m&(+/@:,@:*);._3 ]'
SOBELY =: (, 0 ,: -)1 2 1
SOBELX =: |: SOBELY
FILTEREDIMAGE =: (1 ngm 4) FilterArray IMAGE
COMPLEXIMAGE =: (SOBELX FilterArray j. SOBELY FilterArray) FILTEREDIMAGE
CANNY_EDGE_DETECTOR_STEP_2 =: |COMPLEXIMAGE
ORIENTATION =: 12 o. COMPLEXIMAGE NB. circle function 12 is the angle
of the complex number
NB.xxxxxxxxxxxxxxxxx
NB.TAU =: 2p1 NB. http://tauday.com/
NB.(1 2 3%8)I.ORIENTATION (((] | +) -:) % ]) TAU NB. 0 to 0.5
On Wed, 2013-04-24 at 12:00 +0000, [email protected]
wrote:
Date: Wed, 24 Apr 2013 13:23:16 +0200
From: Sarah Arnold<[email protected]>
To: [email protected]
Subject: [Jchat] J for Image Processing
Message-ID:<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi
I'm new to J (and virtually to programming in general). I have just
finished reading the J Primer. For my PHD I need to do some image
processing. I was wondering whether J was a good choice for image
processing, since the language works so fine with arrays. At the
moment,
I'm mostly using Wolfram Mathematica, which I like a lot, but it is
also
very slow.
Is J fast? Does there already exist a library for image processing
tasks?
Any help is appreciated!
Sarah
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