How to detect certain pixel value in a stick.

Question

Chathurika Sandamali 2021-2-19

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/750169-how-to-detect-certain-pixel-value-in-a-stick

评论： Chathurika Sandamali 2021-2-22

I want to measure the diameter of cinnamon sticks. I already did edge detection. I want to get one pixel value from upper line and second pixel value from lower line and then substract and get the diameter.

I am troubling when get upper and lower lines pixel values.It should be auto detecting when upload an image.

Thank you.

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Answer 1

Rik 2021-2-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/750169-how-to-detect-certain-pixel-value-in-a-stick#answer_627804

Something like this will do it:

A=imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/524729/image.png');
%convert image back to logical mask
L=im2double(im2gray(A))>0.5;
width=zeros(size(L,2),1);
for n=1:size(L,2)
    tmp=L(:,n);
    tmp=diff([find(tmp,1,'first') find(tmp,1,'last')]);
    tmp=sort([0 tmp]);tmp=tmp(end);%catch empty case
    width(n)=tmp;
end
width=median(width);
disp(width)
    15

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Rik 2021-2-22

If it works, please consider marking my answer as accepted answer.

The easiest way to repeat a process in Matlab is to use a loop. You can easily put my code in a function:

function width=WidthOfContour(L)
width=zeros(size(L,2),1);
for n=1:size(L,2)
    tmp=L(:,n);
    tmp=diff([find(tmp,1,'first') find(tmp,1,'last')]);
    tmp=sort([0 tmp]);tmp=tmp(end);%catch empty case
    width(n)=tmp;
end
width=median(width);
end