Edge detection of a nail

Question

Muzammil Mumtaz 2014-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/158146-edge-detection-of-a-nail

评论： Image Analyst 2014-10-12

I am working on a assignment in which i have to detect the edges of nail. i tried to do this using bwboundaries command i did my work to some extent but the problem is that it detected the boundary of the large circle as well. however i just want to detect the nail edges. is there anyway by which i can do this ?

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Answer 1

Mohammad Abouali 2014-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/158146-edge-detection-of-a-nail#answer_154717

编辑：Mohammad Abouali 2014-10-10

在 MATLAB Online 中打开

reverse your mask (so the big black circle becomes white) then calculate the convex hull of that using (bwconvhull). This gives you the entire circle.

Then mask your original mask with the convex hull of your circle, this would set the outer perimeter to black.

Then use your method to get the boundary again.

I downloaded the image you posted and something like this will happen

I=imread('~/Desktop/lateralview.jpg');
I=double(rgb2gray(I))/255; % The image that I downloaded was rgb image. You might be able to skip this step.
Mask=logical(round(I));
bigCircleMask=bwconvhull(~Mask);
newMask=bwmorph(and(Mask, bigCircleMask),'majority');

This is the mask of big circle.

This is the new mask of the nail.

Now use your own algorithm to detect the edges of the nail.

If you want you can go one step further and fit a circle using imfindcircle of matlab to get a better circular mask of the bigCircle.

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Muzammil Mumtaz 2014-10-11

Sir i tried your code and came up with this after modification. And the code worked really well and i have achieved my objective but yes this circles near the nail are being overlapped the nail boundary. But that is kind of ok for me. Here i would need a bit more of your favor with the code as i dont know about few commands what they are doing. Kindly comment them so i understand whats goin on behind the script.

This is the code:

clc; clear all; close all; I=imread('centroid.png'); z=I; I=double(rgb2gray(I))/255; % The image that I downloaded was rgb image. You might be able to skip this step. Mask=logical(round(I)); % KINDLY COMMENT THIS bigCircleMask=bwconvhull(~Mask); % KINDLY COMMENT THIS newMask=bwmorph(and(Mask, bigCircleMask),'majority'); % KINDLY COMMENT THIS newMask = bwareaopen(newMask,200); % KINDLY COMMENT THIS b=figure,imshow(newMask);

[B,L] = bwboundaries(newMask,'noholes'); % KINDLY COMMENT THIS figure,imshow(label2rgb(L, @jet, [.5 .5 .5])); % KINDLY COMMENT THIS figure,imshow(z);

hold on

for k = 1:length(B) % COMMENT boundary = B{k}; % COMMENT plot(boundary(:,2), boundary(:,1), 'g', 'LineWidth', 2) end

hold off

Image Analyst 2014-10-12

Read this: http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

The convex hull is like you put a rubber band around your region.

bwboundaries gives you a cell array, where each cell is an outline. They have to be cells because each outline has a different length. See the FAQ: http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F Saying boundary = B{k}; extracts that one particular boundary so that you can pass it into plot and display it as an outline over the image.

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