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POCan't get clean output in my MATLAB implementation of Canny-Deriche
 

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  1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
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    <p>My code so far is:</p> <pre><code>function imgg = derichefilter1(x, k, a, b, c) osize = size(x); x = double(x); a = double(a); b = double(b); c = double(c); k = double(k); y1 = zeros(osize(1),osize(2)); y2 = zeros(osize(1),osize(2)); y1(:,1) = a(1)*x(:,1); y1(:,2) = a(1)*x(:,2) + a(2)*x(:,1) + b(1)*y1(:,1); for ii=3:osize(2) y1(:,ii) = a(1)*x(:,ii) + a(2)*x(:,ii-1) + b(1)*y1(:,ii-1) + b(2)*y1(:,ii-2); end y2(:,osize(2)-1) = a(3)*x(osize(2)); for ii=(osize(2)-2):-1:1 y2(:,ii) = a(3)*x(:,ii+1) + a(4)*x(:,ii+2) + b(1)*y2(:,ii+1) + b(2)*y2(:,ii+2); end imgg = c*(y1+y2); function imgg = derichefilter2(x, k, a, b, c) imgg = derichefilter1(x,k,a(1:4),b,c(1)); imgg = (derichefilter1(imgg',k,a(5:8),b,c(2)))'; function [mask magn] = nonmaxsupp(x, y) magn = sqrt(x.^2 + y.^2); argu = atan2(y,x); argu = argu/pi*4; argu = int32(round(argu)); argu(argu == 4) = 0; argu(argu &lt; 0) = argu(argu &lt; 0) + 4; mask = boolean(zeros(size(x))); for ii = 2:(size(x,1)-1) for jj = 2:(size(x,2)-1) switch argu(ii,jj) case 0 mask(ii,jj) = (max(magn(ii,jj+1),magn(ii,jj-1)) &lt;= magn(ii,jj)); case 1 mask(ii,jj) = (max(magn(ii-1,jj+1),magn(ii+1,jj-1)) &lt;= magn(ii,jj)); case 2 mask(ii,jj) = (max(magn(ii-1,jj),magn(ii+1,jj)) &lt;= magn(ii,jj)); case 3 mask(ii,jj) = (max(magn(ii+1,jj+1),magn(ii-1,jj-1)) &lt;= magn(ii,jj)); end end end function imgg = hystthres(x,Tl,Th) imgg = (x&gt;Th); limg = (x&gt;=Tl); osize = size(x); nTh = 0; for ii = 1:osize(1) for jj = 1:osize(2) if imgg(ii,jj) nTh = nTh + 1; end end end c = zeros(1,nTh); r = zeros(1,nTh); nTh=0; for ii = 1:osize(1) for jj = 1:osize(2) if imgg(ii,jj) nTh = nTh + 1; c(nTh) = ii; r(nTh) = jj; end end end imgg = bwselect(limg,r,c,8); function imgg = derichecomplete(x, alph, Tl, Th) k = (1 - exp(-alph))^2/(1 + 2*alph*exp(-alph) - exp(-2*alph)); as = zeros(1,8); as(1) = k; as(2) = k*exp(-alph)*(alph-1); as(3) = k*exp(-alph)*(alph+1); as(4) = -k*exp(-2*alph); as(5:8)=as(1:4); b = zeros(1,2); b(1) = 2*exp(-alph); b(2) = -exp(-2*alph); cs = [1,1]; ax = [0,1,-1,0,as(5:8)]; cx = [-(1 - exp(-alph))^2,1]; ay = [ax(5:8),ax(1:4)]; cy = [cx(2) cx(1)]; deriches = derichefilter2(x, k, as, b, cs); derichex = derichefilter2(deriches, k, ax, b, cx); derichey = derichefilter2(deriches, k, ay, b, cy); [mask mag] = nonmaxsupp(derichex, derichey); mag(~mask) = 0; imgg = hystthres(mag,Tl,Th); clc; clear all; close all; imagepath = input('Enter the image path in single quotes: '); alph = input('Enter the value of alpha to be used: '); Tl = input('Enter the value of Tl to be used: '); Th = input('Enter the value of Th to be used: '); imgg = imread(imagepath); szzz = size(size(imgg)); if szzz(2) == 3 osize = size(imgg); hystf = boolean(zeros(osize(1:2))); for ii=1:3 hystf = hystf | derichecomplete(imgg(:,:,ii),alph,Tl,Th); end else hystf = derichecomplete(imgg,alph,Tl,Th); end imshow(hystf); </code></pre> <p>My output on the image on the <a href="http://en.wikipedia.org/wiki/Deriche_edge_detector" rel="nofollow noreferrer" title="Deriche edge detector - Wikipedia">Canny-Deriche Wikipedia page</a> <img src="https://i.stack.imgur.com/hNOlK.jpg" alt="Image"> <img src="https://i.stack.imgur.com/jXM23.png" alt="enter image description here"></p> <p>I can't seem to find an error because I followed the instructions there and on the <a href="http://en.wikipedia.org/wiki/Canny_edge_detector" rel="nofollow noreferrer" title="Canny edge detector - Wikipedia">Canny edge detector</a> page to the letter. I've just implemented the algorithm as it is, and still can't seem to produce the same output. The features are thick and edgy, instead of smooth as on the Wikipedia pages.</p> <p>EDIT: <a href="https://dl.dropbox.com/u/35186704/Deriche.zip" rel="nofollow noreferrer">Dropbox link</a> to code/image so you don't have to copy/paste it. </p>
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      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USHameer Abbasi
    1. USHameer Abbasi
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
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    1. VO
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. This table or related slice is empty.
      1. VTUpMod
    1. COHow did you define `boolean`? It's not a built-in function, so I substituted `logical` and got a different result altogether. Are you using the same parameters (1.5, 20, 40)?
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. USEmre
    2. COAs @Emre mentioned `logical` is the proper matlab command to cast variables as booleans. However, note that for initializing variables you can also just use `false(size)` rather than `logical(zeros(size))`
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. USDennis Jaheruddin
    3. CO@Emre, I did use exactly the same parameters. I'll try logical, and also Dennis' solution.
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      1. POCan't get clean output in my MATLAB implementation of Canny-Deriche
      1. USHameer Abbasi
 

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