How to find length or perimeter of a irregular boundary

Question

Gopichandh Danala 2016-9-1

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https://ww2.mathworks.cn/matlabcentral/answers/301666-how-to-find-length-or-perimeter-of-a-irregular-boundary

评论： Akshay Rao 2017-6-30

Hi,

I work with medical images for some application I have to segment tumors out of CT slices then compute the length of the boundary.

I did the segmentation part and computed the boundaries of slices now how can I compute the perimeter of that boundary. I added a tumor boundary slice for reference. More Info:

These Dicom images even come with pixel spacing which is the distance between each pixel lets say pixelSpacing is 0.7mm Now I have to compute the perimeter length respect to pixel spacing

Please give me some ideas about this

Thanks Gopi

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Answer 1

KSSV 2016-9-2

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https://ww2.mathworks.cn/matlabcentral/answers/301666-how-to-find-length-or-perimeter-of-a-irregular-boundary#answer_233533

If you have boundary in hand....calculate the distances of successive points and sum up...wont his give perimeter?

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Gopichandh Danala 2016-9-2

在 MATLAB Online 中打开

Yes, u r correct Thanks.I was initially worried about diagonal and adjacent pixels in the boundary but I figured it out. posting the code for reference if anyone needs it

The code for this is:

boundary_dist = 0;

BW = thisBinaryImage;

B = bwboundaries(BW);

imshow(BW, [min(min(BW)) max(max(BW))]); hold on;

for k=1:length(B)

boundary = B{k};
cidx = mod(k,length(colors))+1;
plot(boundary(:,2), boundary(:,1),...
     colors(cidx),'LineWidth',2);
end
hold off;
for i = 1:length(boundary)
   if i ~= length(boundary)
       pixel1 = boundary(i,:);
       pixel2 = boundary(i+1,:);
   else
       pixel1 = boundary(i,:);
       pixel2 = boundary(1,:); % when it reaches the last boundary pixel
   end
   pixel_dist = ((pixel1(1,1) - pixel2(1,1)).^2 + (pixel1(1,2) - pixel2(1,2)).^2).^0.5;
   boundary_dist = boundary_dist + pixel_dist;
end
display(boundary_dist)
Output:
boundary_dist =
          97.3969696196699