How to measure a crack length (using skeleton function)?

Question

Thomas Bainbridge 2020-10-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/620133-how-to-measure-a-crack-length-using-skeleton-function

评论： Image Analyst 2022-1-16

I am trying to calculate the length of the crack (attached) however I can't figure out a way to remove the extra sections of the skeleton that branch off from the main crack path - crackoverlay.png.

Does anyone have any advice as to how I could do this?

clc
clear variables
RGB = imread('crack2.jpg');                                                % Aquires original image
I = rgb2gray(RGB);                                                         % Creates greyscale image
BW = imbinarize(I,'global');                                               % Binarises it
BW2 = ~(bwmorph(BW,'majority',Inf));                                       % Fills in holes
BW3 = bwmorph(BW2,'skel',Inf);                                             % Reduces image to center areas of the white sections
BW4 = bwmorph(BW3,'spur',Inf);                                             % Removes spurs
Ov = imfuse(RGB,BW4);                                                      % Overlay of original image and skeleton
figure('Name','All_Steps')
subplot(3,2,1), imshow(RGB), title('Original Image')
subplot(3,2,2), imshow(BW) , title('Binarised Image')
subplot(3,2,3), imshow(BW2), title('Binarised Inverted')
subplot(3,2,4), imshow(BW3), title('Skeleton')
subplot(3,2,5), imshow(BW4), title('Simplified Skeleton')
subplot(3,2,6), imshow(Ov),  title('Overlay')

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Adam Danz 2020-10-22

Well done! Perhaps you could share your solution as an answer. I'd be interested in seeing it.

Thomas Bainbridge 2020-10-22

Thanks - Ive uploaded my code as an answer along with a hyperlink to a MATLAB blog that had a lot of useful information.

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Answer 1

Thomas Bainbridge 2020-10-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/620133-how-to-measure-a-crack-length-using-skeleton-function#answer_521368

在 MATLAB Online 中打开

Here is my solution code.

Thanks to Adam Danz for the pointers.

Blog with useful code

clc
clear variables
RGB = imread('crack2.jpg');                                                % Aquires original image
I = rgb2gray(RGB);                                                         % Creates greyscale image
BW = imbinarize(I,'global');                                               % Binarises it
BW2 = ~(bwmorph(BW,'majority',Inf));                                       % Fills in holes
BW3 = bwmorph(BW2,'skel',Inf);                                             % Reduces image to center areas of the white sections
BW4 = bwmorph(BW3,'spur',Inf);                                             % Removes spurs
Ov = imfuse(RGB,BW4);                                                      % Overlay of original image and skeleton
imshow(BW4)                                                                % Displays the skeleton de spurred
y1 = 151;                                                                  % Start of crack co-ordinates
x1 = 23;    
y2 = 169;                                                                  % End of crack co-ords
x2 = 307; 
hold on
plot(x1, y1, 'g*', 'MarkerSize', 15)                                       % Puts * at location of start and end of crack
plot(x2, y2, 'g*', 'MarkerSize', 15)
hold off
D1 = bwdistgeodesic(BW4, x1, y1, 'quasi-euclidean');
D2 = bwdistgeodesic(BW4, x2, y2, 'quasi-euclidean');
D = D1 + D2;
D = round(D * 8) / 8;
D(isnan(D)) = inf;
skeleton_path = imregionalmin(D);                                          % Returns regional minima 
P = imoverlay(BW4, imdilate(skeleton_path, ones(3,3)), [1 0 0]);
imshow(P, 'InitialMagnification', 200)
hold on
plot(x1, y1, 'g*', 'MarkerSize', 15)                                       % Start position marker
plot(x2, y2, 'g*', 'MarkerSize', 15)                                       % End poisition marker
hold off
path_length = D(skeleton_path);                                            % Path length calculation
path_length = path_length(1)
figure('Name','Montaged')                                                  % Montage of stages 
montage({RGB, BW, BW2, BW3,BW4, Ov})
figure('Name','All_Steps')
subplot(3,2,1), imshow(RGB), title('Original Image')
subplot(3,2,2), imshow(BW) , title('Binarised Image')
subplot(3,2,3), imshow(BW2), title('Binarised Inverted')
subplot(3,2,4), imshow(BW3), title('Skeleton')
subplot(3,2,5), imshow(BW4), title('Simplified Skeleton')
subplot(3,2,6), imshow(Ov), title('Overlay')
figure('Name','Reduced')
subplot(2,3,1), imshow(RGB), title('Original Image')
subplot(2,3,2), imshow(BW2), title('Binarised Inverted')
subplot(2,3,3), imshow(BW4), title('De-Spurred Skeleton')
subplot(2,3,4), imshow(Ov),  title('Overlay')
subplot(2,3,6), imshow(P),   title('Path on Skeleton')