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POpython separate round particles by offsetting contours / shrinking polygones
 

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  1. POpython separate round particles by offsetting contours / shrinking polygones
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    <p>I'm new to python and stuck.. </p> <p>I want to make a python script that allows me to separate adjacent particles on an image like this:</p> <p><img src="https://i.stack.imgur.com/JPh65.png" alt="BEFORE"></p> <p>into separate regions like this:</p> <p><img src="https://i.stack.imgur.com/tePPD.png" alt="AFTER"></p> <p>I was suggested to use the watershed method, which as far as I understand it would give me a something like this:</p> <p><img src="https://i.stack.imgur.com/Jw95W.png" alt="Watershed in 3D"></p> <p><strong>EDIT</strong> <em>Actually found out that this is distance transform and not watershed</em></p> <p>Where I then could use a threshold to separate them.. Followed this <a href="https://stackoverflow.com/questions/11294859/how-to-define-the-markers-for-watershed-in-opencv/11438165#11438165">openCV watershed guide</a> but it only worked to cut out the particles. Was not able to "transform" the code to do what I want.</p> <p>I then took another approach. Tried to use the <a href="http://opencvpython.blogspot.in/2012/06/hi-this-article-is-tutorial-which-try.html" rel="nofollow noreferrer">openCV contours</a> which gave me good contours of the particles. I have then been looking intensively for an easy way to perform polygon offset in order to shrink the edge like this:</p> <p><img src="https://i.stack.imgur.com/Nup0i.gif" alt="Edge offset"></p> <p>Using the center from the offset contours (polygon) should give me the number of particles.. But I just haven been able to find a simple way to do edge offset / polygon shrinking with python.</p>
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    1. COYou might be interested by : http://stackoverflow.com/questions/10313602/reshaping-noisy-coin-into-a-circle-form/10324759#10324759 Distance transform might be useful in your case. As far as I understand it, polygon shrinking could be equivalent to thresholding the distanceMap, no ?
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      1. POpython separate round particles by offsetting contours / shrinking polygones
      1. USQuentin Geissmann
    2. CO+1 for Quentin link, distanceTransform is what you are looking for and the example is very similar to your problem
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      1. POpython separate round particles by offsetting contours / shrinking polygones
      1. USremi
    3. COThe distance transform acutually got me very far, but then @Nicolas Barbey posted a really nice and easy solution.
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