Image processing for crack detection and length estimation

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Hi, I have written the following matlab code to do the following:-
  • load rgb image of surface
  • contrast stretch
  • convert rgb to gray scale
  • image segmentation
  • morphological operations (thin, clean , fill, etc...)
  • imtool for pixel length determination
  • Calculation of crack length based on calibration of image and above determined pixel lenght.
My aim is to develop the SIMPLEST matlab code for automatic detection of cracks and estimate the length of the crack (if possible other geometrical properties) from a sample image.
The code is shown below:
%%load image
title('Original image')
%%Image adjust
Istrech = imadjust(I,stretchlim(I));
title('Contrast stretched image')
%%Convert RGB image to gray
Igray_s = rgb2gray(Istrech);
title('RGB to gray (contrast stretched) ')
%%Image segmentation by thresholding
%use incremental value to run this selection till required threshold 'level' is
level = 0.08;
Ithres = im2bw(Igray_h,level);
title('Segmented cracks')
%%Image morphological operation
BW = bwmorph(gradmag,'clean',10);
title('Cleaned image')
BW = bwmorph(gradmag,'thin', inf);
title('Thinned image')
BW = imfill(gradmag, 'holes')
title('Filled image')
%%Image tool
%%Calaculate crack length
crack_length=(crack_pixel *calibration_length)/calibration_pixels;
Please, I need help from image specialist to improve the code from above to meet my aim. I have also attached a sample picture that I am using for this code.
Picture two.jpg is attached below:

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Accepted Answer

Image Analyst
Image Analyst on 9 Apr 2015
You're just arbitrarily setting
You're not even doing it manually (with user assistance) - you're just setting some arbitrary number. What's up with that? If you need code to find the distance between the farthest points in a binary blob, see my attached demo.
Image Analyst
Image Analyst on 7 May 2022
@Pilli Lalvinnu, sure. What sort of help do you need? I'm assuming you started with the solutions given here but they didn't work for your image(s) so start a new question with your code and images attached, and ask a specific question and we'll help.

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More Answers (4)

Dan on 13 Apr 2015
I just glanced at your code and if you need a completely automated system, you need to either define what constitutes a crack beforehand OR have the system learn these rules using something like a neural net.
But... that's a bigger project. In the short term, you might want to play with the graythresh function that will automate your selection of a threshold.
Just my $0.02.
  1 Comment
BB BSB on 14 Apr 2015
Edited: BB BSB on 14 Apr 2015
I see, for timeline limits Id rather attempt the easier of the 3 methods you outlined which I guess is playing around with graythresh function.
Any hints as to how or what to look out for in doing so? Because my first approach would be to scale by a factor??? make any sense? Thanks.

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Yashwanth G M
Yashwanth G M on 25 Mar 2019
Sir help me to find out the area of a solar panel interms of

Ram kumar R
Ram kumar R on 12 Feb 2020
i got error in line no.21 as Ithres = im2bw(Igray_h,level) can u explain it ?
Image Analyst
Image Analyst on 28 Feb 2021
@Ayoub MOSSLIH, we have no idea what code you ran. Please start a new question and attach your image and m-file there.

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Image Analyst
Image Analyst on 2 Jan 2021
See my attached demo that computes both the tortuosity and mean width.
Image Analyst
Image Analyst on 8 Jun 2021
So your technical university really assigns you an image processing programming task, doesn't give you any training on programming by your final year, and allows you to ask strangers/others to program it up and give it to you to turn in their code as your own? I've never heard of a university like that. In fact, most would land you in serious trouble for doing that. Maybe you can ask them to give you a different task - one you can complete by yourself. Because, sorry, but we're not going to go to all the work of programming it and giving it to you. The Mathworks would but of course they would charge a consulting fee since it will take their valuable time. The best I can suggest are these two links:
MATLAB Academy - Free 2 hour training Image Segmentation Tutorial
With about 4 hours work looking over those two web pages, you should easily be able to modify my Image Segmentation Tutorial to work with your images for simple images.

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