How can i detect the boundary using bwtraceboundary function ??

Question

Surendra Ratnu 2023-5-1

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https://ww2.mathworks.cn/matlabcentral/answers/1955724-how-can-i-detect-the-boundary-using-bwtraceboundary-function

回答： Image Analyst 2023-5-5

I want to detect the seperate two boundaries (inner and outer boundary) in our case.. I want to seperately detect inner and outer boundary and calculate the distance between them along the boundaries. In the image.png, I shown the exmple how will i want to do seperate the boundary (red and green colour boundary) which i want to seperate into inner and outer boundary. please give me a solution so i can automatically select the starting point and store the boundary data into two matrix.

Thank you for help

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Answer 1

Antoni Garcia-Herreros 2023-5-2

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https://ww2.mathworks.cn/matlabcentral/answers/1955724-how-can-i-detect-the-boundary-using-bwtraceboundary-function#answer_1227364

在 MATLAB Online 中打开

Original_image (2).png

Hello Surendra,

You can take a look at this thread.

But the general idea would be to:

Crop ROI
Segment your image
Obtain the boundaries and calculate thickness

clear all

close all

I=imread('Original_image (2).png');

%% Crop region

Icrop=I(1:720,400:600);

%% Segment

BW=~imbinarize(Icrop);

se = strel('disk',5);

BWc=imclose(BW,se);

skelImage = bwskel(BWc, 'MinBranchLength', 10); % First guess. Strangely bwskel() doesn't seem to have any short spurs, no matter what MinBranchLength is.

imshow(imoverlay(BWc, skelImage, 'r'));

title('Binary image with skel')

%% Obtain distances

edtImage = bwdist(~BWc); %Distance of to nearest 0 value

radii = edtImage(skelImage); % Extract the distances only along the skeleton

% These are the half widths. Multiply by 2 to get the full widths.

averageWidth = 2 * mean(radii)

averageWidth = single 11.9689

%% Find the boundaries

E=edge(BWc); % Find the edges

CC = bwconncomp(E); % Isolate the different components

[rowOut1,colOut1]=ind2sub(size(E),CC.PixelIdxList{1,1});

Pout1=[rowOut1,colOut1]; % Pixels forming Outer boundary 1

[rowIn,colIn]=ind2sub(size(E),CC.PixelIdxList{1,2});

Pin=[rowIn,colIn]; % Pixels forming Inner boundary 1

[rowOut2,colOut2]=ind2sub(size(E),CC.PixelIdxList{1,3});

Pout2=[rowOut2,colOut2]; % Pixels forming Outer boundary 2

figure(2)

imshow(BWc)

hold on

plot(Pin(:,2),Pin(:,1),'.','MarkerSize',2)

plot(Pout1(:,2),Pout1(:,1),'.','MarkerSize',2)

plot(Pout2(:,2),Pout2(:,1),'.','MarkerSize',2)

title('Boundaries')

Hope this helps

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Image Analyst 2023-5-5

Then why did you accept the answer? It's not how I would have done it. I don't know whether to give you my solution or not -- maybe you've already solved it yourself since it's rather easy if you use bwboundaries instead of bwtraceboundary. Let me know if you need my solution.

Surendra Ratnu 2023-5-5

Hi Image Analyst.... I used bwboundaries instead of bwtraceboundary but in bwbouries it dectect all boundaries but i need to trace inner and outer boundary seperately and need the co-ordinate of the inner and outer boundary seperately. Please give me the your solution it will be great help for me. Can you just eloborate on " how to seperate the inner and outer boundary seperately using bwboundries ??".

Thank you for your answer.

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