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Image Segmentation Tutorial

version (6.57 KB) by Image Analyst
Image Processing Tutorial to demonstrate the basic concepts to beginner users.


Updated 03 Apr 2015

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This file was selected as MATLAB Central Pick of the Week

Perfect for the beginner, this demo illustrates simple object detection (segmentation, feature extraction), measurement, and filtering. Requires the Image Processing Toolbox (IPT) because it demonstrates some functions supplied by that toolbox, plus it uses the "coins" demo image supplied with that toolbox. If you have the IPT (you can check by typing ver on the command line), you should be able to run this demo code simply by copying and pasting this code into a new editor window, and then clicking the green "run" triangle on the toolbar.
First finds all the objects, then filters results to pick out objects of certain sizes. The basic concepts of thresholding, labeling, and regionprops are demonstrated with a simple example.

It's a good tutorial for those users new to MATLAB's image processing capabilities to learn on, before they go on to more sophisticated algorithms.

Tested with R2008b through R2011b.

Cite As

Image Analyst (2021). Image Segmentation Tutorial (, MATLAB Central File Exchange. Retrieved .

Comments and Ratings (237)

Guillermo Quintas

Aman Gupta

Joel Silva


kamred udham singh

Syukri Yazed

I've tried your code and learn basic for image processing. However, when I tried to use my image (4 shapes image) in rgb, the code cannot detect the shapes. The code only detect the shape of the image; but not the 4 shapes in the image. The code is definitely convert the rgb to gray, but somehow it not detect the shapes. So, I try to originally convert the input image to gray first. Then, I process it into the code. It was successful. The code detect the 4 shapes correctly.

@Image Analyst,
could you give your comment on this matter?

Arthur Paris

Ali alshamrani

If I have my own images, how to put them in the code? Does the code find the center mass of each image?


dolly indra

Your tutorials and answers are very helpful. I like it

Bartosz Olborski

"Attempt to execute SCRIPT regionprops as a function:
Error in BlobsDemo (line 140)
blobMeasurements = regionprops(labeledImage, originalImage, 'all'); "

Miranda Lynch

Incredibly helpful

Alon Zaharony

Tony Dib


Respected Image Analyst, Your tutorials and answers are very helpful. Every time it saves me. Sir I am looking for code for below algorithms (any one/two will be fine)

1. Improved Local Ternary Pattern.
2. Elongated Local Ternary Pattern.
3. Elongated Local Quinary Pattern.
4. Ensembled of Local Quinary Pattern.

can you please help me aboutthis.

Karthik Kaarunya

van nguyen

Alberto Mora

arezoo kbr

Peiyu Wang

hemanth kappali

can anyone help me out in list of statistical parameters obtained from a segmented image?

Vardas Pavarde

John Montgomery

jemery zhang

sayar chit


Wouter Wesselink

Pramukha Thimbiripola

José Antelo Zamora

Diah Junaidi

Praveen Manupati

Renee Chow


Trung Nguyen Huu


Fizza Zahid

Umar Farooq Ghumman

Jeff Severino

Farnaz Gh


Dear Image Analyst, Your tutorial is very useful. As a beginner to image analysis, it helped me understand how to segregate relevant sections of my images and analyze my data. I used your script as part of my data analysis. Please let me know how I can reference your code in my publication.Thanks for your help!

Zanetta Liu

Image Analyst

safina, image processing algorithms need to be adapted to the images. Whether it will work on your specific coins is just something you have to test.
vv_art, if you have questions about specific image processing algorithms, ask them in the Answers forum, not here. There we can give you a proper answer, something I can't do in the brief comment section here. Thanks.



dear sir.
Currently i am working on detection of different colors in a resister using image processing.But, I am unable to do this for all images and all colour detection.Please help how to approch.if possible please send me the code sir.

Thank you


Ali Buendia

Naimul Hassan

safina yousaf

Could we run this code for different images of coins? Surely it will run on them?? Does Quality of picture matter?


Sakara Somapa

Thanks alot! segmenting by thresholding dark regions was surprisingly hard to track down online but yours works like a charm!

Samia Ahmed

Hina Maqsood

Liliana Malik

Thank you so much this is really great, i want to know how to apply this to an image ?

Eliana Marin

Madhura Guha


Thank you so much! How would i apply this to a video?

Javier Garcia

Girvani Manoharan

Dear Image Analyst,

Your tutorial on image segmentation was a great help. I have ran into a following problem and wonder whether you can guide me. I have a segmented image which contains a part of the rock which consisted the fractured area and also the white corner regions. I want to calculate the total no of white pixels within the dark region (i.e no of fractured pixels). How can I do that avoiding the corner white areas.Much appreciated.

Image Analyst

Svetlana, look in the Answers forum for "Spatial calibration" because I've posted code for converting pixels into real world units such as mm.

zhang xiaorui

Svetlana Zeveleva

The area you get are in units pixels ... I'm using a microCt scout image and need to find areas of similar shapes but in mm units. Do you have an idea of how I can achieve this?

haniz azwa

Hi image Analyst-this code was really helpful. Anyway, i am currently working on my final year project, and i am using your coding to detect normal cell and sickle cell. The coding work perfectly, however, it didn't detect the sickle cell. May i know what is your parameter value? and which part should i adjust the value of the parameter

Asma Shahid

Hi Image Analyst - this code is really very helpful. thanx

Prajwal Ainapur


plz clarify me one thing that for the purpose of image segmentation, if we use matlab function ( regionprops) then is this any algorithm? or just a function


Siv-Marie McDougall

Joe Perkins

Hi Image Analyst - I thought this might be the case. How would one change the pixel values to black or white?

Many thanks for your help, Joe

Nurzalina Harun

Varun K N

hello sir,
can we save the different coins separately into a folder??if yes,Can you explain how with a code

Image Analyst

Joe Perkins, images must remain rectangular so the coins MUST have some background outside the round regions of the coin itself. All you can do is to change the background, not remove it. You can have this either the original background, or some uniform intensity like black, white, or some gray level.

Benjamin Baynard

Can this script be used to count black or white pixels of an image? I was trying to identify if I could do that by looking at the code but I'm not sure due to the complexity of this example.

Diah Junaidi


Joe Perkins

Hi Image Analyst,

Brilliant demo thank-you!

How would you go about separating the coins in the final images from the background around them so that the output images contain the coins only?

Many thanks,


Joe Perkins

qifeng li

abdul basir

Rui Pais

Serhan Gül

Boson Saya



Arthur Gallina

Suresh Kumar Jetti

Dear Image analyst,

Thank you very much for the codes again. I am a neuroscientist from MIT and I'm really impressed by your recent code. I have an example neural calcium imaging tiff file (stack a tiff files from one video). I have to extract calcium signals (peaks, ROIs) from individual synaptic site. The goal is to map the synapses when they are active. I really believe that your code can solve of my problem. Could you please help more in this regard?

Thank you so much,

Kind regards

Suresh Kumar Jetti

I really enjoyed this code. I have some back ground in image analysis yet these codes are very informative.
Please post more advance example as well. Thank you

xuan du

Good demon to novice like me. Thanks alot


Hello Image Analyst, I am going to do some analysis on an image and i need to write a code to recognize the coordinates of different points of red color automatically without human interfering. I will be grateful if you propose some methods. Thanks in advance.

preethika sanil

Ken Cheung

Nice job.Thanks for your sharing.


Nice tutorial. Thank you

andhavarapu lokesh

sairam to all members ,
can anyone give me the code of otsu thresolding for applying on to thyroid dicom images

Robert Garnett


I did it the hard way until I saw this and then it was so-easy.


Aaron Greenbaum

srijan sharma

Steve Cohen

Tim-Van Ho


ainzul hafiz


Manu BN

Awesome work. Inspired by you I have also uploaded 13 of my projects for sharing knowledge. Plz checkout

Himanshu Tyagi

anyone help me? In my thesis work on content image retrieval using HSV CCV and LBP ..please provide me email id if possible mine is

Ashok Tripathi

Quite helpful. And so nicely documented.

arrjun balaratnam

Hello, I currently have an image of the veins binarized. I've tried using parts of your code so that i could then find the coordinates of the the edges/nodes of the image but have had no luck. Any tips would be appreciated.

Image Analyst

If anyone has specific questions about how to adapt this demo to their specific image, post the image and problem description to the Answers forum here on the Mathworks website.

haider alnaqeeb

hello dear i need your kind support to find the center of an object in a binary image in order to i can crop that object from the binary image, note that the binary image has only one object no more so that ow can i determine the center of that object



Thanks, the file helped me to understand segmentation.

How can same be used with the DICOM images? Can you help me with the feature extraction of the images?

Nasr Gharaibeh

Mugabi Samuel

Wow; I agree you are the best teach at Image analysis and processing; This tutorial helped me a lot indeed THANK YOU VERY MUCH;

I would like to learn from you more as I also approach my project; Please write to me at:

So I can ask you some questions.


askaryaqs askaryaqs

thanks for your sharing, this is helping me

Fatin S

hye. can i ask u some private question on how i can detect the circle like u do but my circle not really circle because the picture i snap was a tennis ball and pingpong ball.can u give me a solution please.i try your coding but it didn't seem work.really need your help.and please email me at if u feel free.tyvm

Nasr Gharaibeh

Excellent, thank you


Image Analyst

Ramses, you just flip the sign of the > sign to < so that it finds dark objects instead of bright objects.

Philip Fischer

Ramses Herrera

How would one handle images where the object intensities are much lower, say segmentation of organs in a CT?

Ramses H.

Pradeep Bhaskar

Thank you, this is excellent.

Raga dinesh

its very useful for me.. thank you..


Thank you for the amazing tutorial. what do i do if i have to extract a certain section from image who's orientation can be anyway.


I have a question,
is there an automatic way to filter the unwanted regions from a binary image , where the wanted regions are character candidates in different scales (sometimes big letters and sometimes small)?
please help me out

marwan saeed


manasvin upadhyay

eyp say

Perfect!!! thank you for sharing.

majed majed

great work !!
thank you a lot.


Ardhi Santoso

Sergei P.

izyan hanum


Nisha S Rani

please send us the code


thank for sharing

Abdur Rahmaan


Thanks a lot for sharing ;)

Akash Ghode

Dakala Jayachandra


Rushikesh Tade

Nice work!

alex yang

Shien Kwun Leong

Dear Image Analyst,

Thank you for this beautiful code. I'm trying to use it for oil palm ripeness detection.

ramin bba

Looks simple and sophisticated at the same time! Full of comments and as such easy to follow the chain of thoughts of the author. One can simply make adjustments based on his/her needs. Great job Image Analyst!



i get an error...please help me.

??? Error using ==> cd
Cannot CD to (Name is nonexistent or not a directory).


Dear Image Analyst,

Thanks for this beautiful code. I have a minor question concerning about the 'keeper' blob image. Is that possible that we segment the keeper blobs while still keep their numbers on it? Like tracing which number of blobs are the brightest and which number are the darkest? How should I write the code?

Thanks for your help!

Yogesh Babu

I used this code to find the Area of the each object this file does,But I am in need of number occurrence of same object should be known and that should be plotted..


Works perfectly - very helpful!!



I also got the same errors as xsfeng when I run it.

Error using fileparts
Too many output arguments.

Error in BlobsDemo (line 191)
[thisFolder, baseFileName, ext, version] = fileparts(thisFile);





Dear Image Analyst,

I got the error information when I run this scripts:

Error using fileparts
Too many output arguments.

Error in BlobsDemo (line 191)
[thisFolder, baseFileName, ext, version] = fileparts(thisFile);

Could you please help me with this? Many thx!

adan flores

ok good programing

Image Analyst

mustafs, the more sophisticated algorithms are more dependent on image content. More complicated content requires more complicated algorithms. I did add some demos on color segmentation, but I want to stick to fairly standard kinds of segmentation since there are an infinite number of unique, peculiar ones.


Mario Garcia

mangood UK

dear image analyst,
can you please make to us more advance segmentation algorithms for different industrial application
the segmentation process is the most hard operation for all

Valeska Pearson

Valeska Pearson

Hello image analyst,

How did you obtain the values to divide between foreground and background, at your thresholding code.

for example, why 70 and 0.94
thresholdValue - 70), double(0.94 * maxYValue(2))

Jean Bilheux

Looking at the code taught me a few new tricks ...very nice.


Awesome, a nice presentation on feature extraction.



This is so helpful. Thank you so much!

brahim ouali


vo danh


Image Analyst

Nina, to do that exactly, you'd need to use John D'Errico's interparc program. Look for it in the File Exchange. You can also subsample, like thisBoundary(1:10:end,2) though these won't necessarily be evenly spaced in distance.


Very useful demo. I do have a question Image Analyst - I hope you see this! For the part of the code:

boundaries = bwboundaries(binaryImage);
numberOfBoundaries = size(boundaries);
for k = 1 : numberOfBoundaries
thisBoundary = boundaries{k};
plot(thisBoundary(:,2), thisBoundary(:,1), 'g', 'LineWidth', 2);
hold off;

Is it possible to plot say only 10 points equally spaced around the boundary? Are they in order say clockwise or anticlockwise?


Very nice, saved me at least one day!

mustafa alnasser


is the actual tutorial available to watch online? cannot seem to locate it.

Image Analyst

If anyone has any questions about their own specific images, they should ask in the Answers forum (look at the menu above). Do not put your specific question here as a comment on this program. I can help there in Answers. This page is not meant to be a discussion forum.


Hello Image Analyst ,

your demo is excatly what I am looking for to analyse my fluorescence images. However my images are taken with a 12 bit peltier cooled fluorescence camera and saved as .tif. I can hence not display their histograms without getting an error:
" Warning: Image is too big to fit on screen; displaying at 67% "

I tried to plot the histogram using

plot_size = get(0,'ScreenSize');
fg1 = figure(1);
set(fg8, 'Color', [1 1 1], 'Position', plot_size, 'Visible', 'on');
[pixelCount grayLevels] = imhist(orginalimage);
bar(pixelCount); title('Histogram of orginalimage');
xlim([0 grayLevels(end)]);

but it didnt help. I would really appreciate any help and comments.


abhinav gupta

Hey this demo has been very project is wavelength calculation using diffraction grating, so we get an image which will be a series of round dots and we should find the distance between two successive with this blob i can find the dots but how to find the centres of those dots?????? plz help me anyone... i would be greatful......ty in advance


Thanks for showing us a basic demo. It helped a lot!


thanks for sharing this demo. This provides a very good example for beginners.


Image Analyst

Christie, when you adapted it, you had it read in a color image, even if it doesn't look like it. Do this to prove: [rows columns NumberOfColorChannels] = size(yourImage). Use rgb2gray() right after you call imread() to convert your color image into a gray scale image.


Hey, Image Analyst,

Sorry, I tried to send this as a message first but kept getting an error from the site. Anyway, I am using your BlobsDemo to find the area of leaf surfaces traced onto a piece of graph paper. The code has no problem translating it into a binary image with clearly defined leaves and no graph paper grid, but when it tries to label each blob I get the following error:

??? Error using ==> iptcheckinput
Function BWLABEL expected its first input, BW, to
be two-dimensional.

Error in ==> bwlabel at 67
iptcheckinput(BW, {'logical' 'numeric'}, {'real',
'2d', 'nonsparse'}, ...

Error in ==> LeafArea at 48
labeledImage = bwlabel(binaryImage, 8); % Label
each blob so we can make measurements of it

What does it mean when it says the image isn't 2-dimensional?

Thanks for your help,



Aliyu Abdu

I'm finding your Demo quite very useful in my work. Thank you.


it's nice info for beginner thank's



Image Analyst

Syahrul, it does do segmentation into several areas - each coin is a different area. How can you label something without having a binary image? You can't, but why would you want to avoid labeling even if you could?

Image Analyst

sivan, you must have a color image for some reason. You probably changed the filename to one of your images. Coins.png that my demo uses is a monochrome (gray scale) image.

Syahrul Niezam

is it possible to do segmentation into several areas, not binarization before labeling?


Image Analyst

If anyone wants to ask me a question, click my name above, then click the "Contact Author" link.


sivan saminathen

can any wan help me...why i got error in the code when i try to run line 41-[pixelCount grayLevels] = imhist(originalImage);...this code..the error said

("??? Error using ==> iptcheckinput
Function IMHIST expected its first input, I or X, to be two-dimensional.")

why it said so...i just keep on follow the code given but suddenly it give error


Hi I appreciate this demo very much. I modify your code to work along with watershed segmentation for my image (blood cell), and it turns out good. However, how do I filter the background after I plot the boundaries of the selected cell? (so that the resulting image only shows the blobs without the background) The cropping works very well too but I don't want to involve the background. Thank you.

Image Analyst

You ask this kind of question on the newsgroup or on Answers, not as a comment on people's File Exchange submissions. I'd be happy to answer it there.

German Espinal

Please I need some help !!! I need to capture a basic color card with my webcam, then I need to determine what color is it. Matlab code analize and gives the answer. Example: The card is yellow. Can someone of you Help me please with the MatLab code ???? TKS A lot !!!

German Espinal

Hi guys !!! I need to capture a primary color card with my webcam, then I need to determine what color is it ??? Can someone of you Help me please with the MatLab code ???? TKS A lot !!!




I should read code comments more thoroughly. No need to answer. Thanks!


thank you



Please can somebody send me the matlab code for gray scale image segmentation plzzzz...?I will be very greatful



I'm pretty new to matlab.Can you offer some help regarding my issue?
I need a code to extract objects from a single image and write the extracted objects to separate images.As an example if an image consists of say an elephant and tree , I want to extract these two objects and write as separate images..


Very cool code.


Image Analyst

Manhal, I used Photoshop to create an image with 12 coins and it worked just fine. You must have done something wrong.

Image Analyst

Vivek, what is it about this that made you think it was a 1 star? Is there anything I could improve with it to help beginners understand it better?


and one more thing, I tried to change the image that is used in the BlobsDemo, by adding 2 more coins, but still show that we already have 10 objects...
is there something should I change to make it works??

Naresh Pai

Useful and well-commented code that demonstrates image thresholding. Connected components, including real world objects, in an image is of interest to many and this code provides the starting point for such projects. Thanks IA.


An excellent demonstration of simple image segmentation. Also a nice introduction to the image toolbox in Matlab. The functions for dealing with connected components (centroid, mean, etc) should be extremely useful.

Vivek Maik

Image Analyst

J.D, you need to get some model of skin color. I know that it's a boomerang- or banana-shaped cluster in HSV color space. You need to define parameters to model that, and then segment it, possibly with a 3D lookup table instead of a mathematical model, or with the mathematical model if you can come up with the formulas. But I know you can't simply do high and low thresholding in any color space to carve out a box that selects the skin color pixels.


hello ~ i juz want to ask you what should i do if i want to recognize color of human skin~ i want to get its hsv value for every pixel of the human face ~ and then exlude the eye and mouth part~ i want to get the value as my input to train in neural network~ can u help me~ urgent.. tq~

Image Analyst

Christopher. Yes there are lots of more complicated images that could be used that would be more challenging. I work with many of those kinds of images. However I know from my newsgroup postings that even code as simple as this blows a lot of people away. So thanks for the suggestion but I think I'll keep it simple. I do have some color demos posted that are slightly more challenging.

Walaa Gouda

Hi I am working in my master about breast cancer mass detection the first step is to determine region of interest which is the breast contour and i need help in this step as i don't know how to do this so please if there is anyone who can help me


i am just trying it


Interesting demonstration ImageAnalyst. Fortunately the 'coins' sample image has high contrasting content which allows for easy selection of the threshold. Plus the coins allow for the 'imfill' operation to perform the majority of the work.

It would be interesting to see results on an image with a much smoother histogram but this is where image segmentation gets complicated I guess...

All in all, a nice demonstration of the capabilities that both the IPT and Mathematical Morphology can provide in image processing applications.



hello every body, can you give me a code for building extraction using mathematical morphologie ?? and thanks a lot


Hi, I've tried your demo but it's not working for 3D images. Is there any way to solve this problem? Thanks

aravind prajan

Image Analyst

Like other submissions that are meant to demonstrate certain toolboxes, you need to have the toolbox. If you don't have it, you can buy it, or write the necessary toolbox functions yourself. Generally they are the functions starting with the letters "im" or "bw".

John Brathwaite

What if I don't have the IPT??

David JL

I just realized I use Matalb R2007b, not R2008. I guess that is the problem. Sorry about that.


Very useful...great work...


great work..I have one question for U. using my web cam i will capture a picture which will contain a ball in a room. now how can i separate the ball (circular shaped) from the background and i want to find the area of that ball(circle). how can i edit your code for this particular task.


Image Analyst

Jimmy - ask in the newsgroup. Let's take this conversation there.


Ok let's forget about GUI, I am not even sure if I need to use it. The reason I asked if I can get more than one image read is than after I modified the code I got my the centroids of all objects in the images. The results are in vector form [x y]. For example
[29 134]. I want to make a loop going through all images and objects in them, reading those measurements. Can you give me an advice? Thank you

Husam Aldahiyat


Image Analyst

Jimmy, just paste whatever code you want into line 1076 of that app after you've deleted lines 1076-1164. Then just run it with the green triangle. You need all the rest of the code because that is the GUI. To select images, you simply click on their names in the listbox like you'd do with any app. No code is needed from you to handle clicking on a listbox - that's already done for you. Just click on the images you want to process and click the analyze button and it will analyze only those that you've clicked on.


Ok I did as you said Image Analyst.I got some errors. Now do I only use 1076 - 1164 code or the whole Magic code which is huge? And another thing how do I select images from a folder? Do I need to put that into the code? Thank you

Image Analyst

Jimmy, just follow these easy step by step instructions.
1. Open both his MAGIC code and my BlobsDemo code in MATLAB.
2. Copy all of my BlobsDemo code into the clipboard.
3. Go to AnalyzeSingleImage in his code, currently line 1075, and simply delete all of that function, which means delete lines 1076 - 1164. This is just like it says to do in the comments on line 1070 and 1071 of his code.
4. Now simply paste in my BlobsDemo code.
Now it should work. Adapt my/your code in that function as you see fit.


Thank you for your reply Image Analyst. Yes, I know that I need to make changes according to the pictures regarding threshold etc.. What I don't understand is how to plug that code into AnalyzeSingleImage(). Is it possible for you to send me the example on Thank you

Image Analyst

Jimmy, sure - just copy the code into your own program. One way to do it might be to use this in conjunction with MAGIC ( which does batch processing. Just take this code and plug it into his AnalyzeSingleImage() function. Then you'll be able to select several images from your folder, and process them. Of course, my code has several things that are special for the coins image and you'd have to modify several things for your images, such as the thresholds, etc.


Great Work Image Analyst, very useful indeed. I want to ask one question: is there any chance that it can be applied to more than one image simultaniously? And if there is how can it be done. Thank you

Image Analyst

Thomas, this is not an error in my code. sprint() is not a function - ParseInputs() should have called sprintf() instead. regionprops() and ParseInputs() are Mathworks code, not mine. I searched the R2008b version of ParseInputs and it no longer has sprint() in it, so they've fixed that bug.

Sorry that I can't test this with every prior version of MATLAB. I know it definitely works with R2008a and later. Since you are several years behind I suggest you get the most modern version of MATLAB.

ThomasKUL Knaepen

Not working for me:

Running BlobsDemo.m...
??? Undefined command/function 'sprint'.

Error in ==> regionprops>ParseInputs at 878
msg = sprint('This measurement is not a string: "%d".', list{k});

Error in ==> regionprops at 114
[L, requestedStats] = ParseInputs(officialStats, varargin{:});

ThomasKUL Knaepen

I got :

MATLAB Version (R14) Service Pack 3
and the IPT


an excellent and exceptionally well commented image processing demo by a seasoned ML user and senior CSSM citizen...

a few changes i'd make:
- put it into a function
-> no need for the bad CLEAR ALL...
- make the figure size smaller -and-
- put an ECHO ON/OFF at the beginning/end of the demo
-> for users to be able to enjoy the comments during run-time...

just a few thoughts

MATLAB Release Compatibility
Created with R2015a
Compatible with any release
Platform Compatibility
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