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POIdentify all co-linear line segments (in matlab)
 

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  1. POIdentify all co-linear line segments (in matlab)
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    <p>I have posted a related but not the same question here <a href="https://stackoverflow.com/questions/8279698/measuring-length-of-dna-fibers-from-an-image-of-single-molecules">https://stackoverflow.com/questions/8279698/measuring-length-of-dna-fibers-from-an-image-of-single-molecules</a></p> <p>Background: I have many images that look like this: <img src="https://i.stack.imgur.com/kX4H3.png" alt="enter image description here"></p> <p>I would like to identify all line segments that are co-linear and then measure the length of these segments. In the image above there are 3 pairs of segments that are on an imaginary line with a negative slope. The line segment that is the longest does not have a pair so it would not be considered i.e. there must be atleast 2 segments that are colinear.</p> <p>I get the following: <img src="https://i.stack.imgur.com/arIIi.png" alt="enter image description here"></p> <pre><code>I = imread('http://dl.dropbox.com/u/18072545/c_39_green.tif'); BW = edge(I,'canny'); [H,T,R] = hough(BW); NUMPEAKS=15; PEAKTHRESHOLD= 80; SUPPRESSNHBR=[40 40]; P = houghpeaks(H,NUMPEAKS,'threshold',PEAKTHRESHOLD,'NHoodSize',SUPPRESSNHBR); MINLENGTH_OF_SEGMENT=50; GAPLENGTH_TO_MERGE=30; lines = houghlines(BW,T,R,P,'FillGap',GAPLENGTH_TO_MERGE,'MinLength',MINLENGTH_OF_SEGMENT); max_len = 0; figure, imshow(I), hold on for k = 1:length(lines) xy = [lines(k).point1; lines(k).point2]; plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green'); plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow'); plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red'); end </code></pre> <p>I had to play around with the parameters in order to get a reasonable performance (though I am unable to find a parameter that will capture the starting bit of the segment that is at the bottom). However, I am unable to avoid finding multiple segments that are overlapping.</p> <p>Can someone please help me 1. Prevent identification of overlapping segments. 2. Identify all the lines that are co-linear</p> <p>Many thanks!</p>
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    1. USCommunity
    1. USLee Sande
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      1. POIdentify all co-linear line segments (in matlab)
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    1. CO(for 2:) could you just pick one segment, find its slope and check for others that are of similar (within some tolerance) slope? I know this doesn't take into account parallel segments, but you could try to use some sort of ROI defined by the slope +/- some tolerance to eliminate other segments from creating false positives.
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      1. USSt-Ste-Ste-Stephen
    2. COHow will you treat a case with 3 co-linear segments, where the first segment and the second segment intersect? Do you need to consider *both* the set containing the first and the third *and* the set containing the second and the third segment?
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      1. UScyborg
    3. CO@cyborg When 2 segments intersect then they are part of the same segment (as such intersection is not common in our experiments). I am not sure however what strategy to use discard one of the two or more intersecting segments. Any ideas?
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      1. USLee Sande
 

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