MATLAB Answers


Dividing the image into blocks

Asked by kash
on 27 Nov 2012
Latest activity Edited by Image Analyst
on 30 Nov 2018
I have a image that I want to divide into blocks until each pixel in block have same value. For example in the link below I have an image
The image consists of waters ,leaves and green parts. I want to keep dividing into blocks until it contains the same value.
Please help.


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on 27 Nov 2012
I do not see any picture on the linked page, but a lot of advertisments.
on 27 Nov 2012
Assuming the value below taken from image
im = 64 65 66 69 69
64 66 68 70 72
64 64 66 67 73
64 62 64 62 67
63 60 62 63 66
64 62 60 63 67
67 63 61 61 65
67 68 67 63 63
In this pixel value 64 has 4 values, so it must be in a block, 63 must be block, 64 must be block, last two 67s must be a block and so on. In 4th and 5th columns 2 values of 69s must be grouped, and so on i.e same pixel value must be in a block
Image Analyst
on 27 Nov 2012
I didn't see a picture immediately either. When I clicked on the download link, my company threw up a page that says they've forbidden us to go to that web site. Please pick a site where we can see the image immediately, like or dozens of others.
What do you mean "grouped" or "in a block"? I think of a block as rectangular - what if your contiguous set of gray levels is not rectangular? Can you have blob-shaped "blocks"? If so are you talking about connected components labeling like done with bwlabel and bwconncomp?

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2 Answers

Answer by Image Analyst
on 27 Nov 2012

kash, I know you've been doing image processing for over a year now and I know you know about bwlabel() and bwconncomp(), so tell me why doing something like
labeled67blobs = bwlabel(grayImage == 67); % Similar for any other number.
is not doing what you want?


on 27 Nov 2012
i saw tour demo at
like that i want to divide as in peppers image,
want to divide into sub image such that wach subimage has same pixel value
on 27 Nov 2012
labeled67blobs = bwlabel(grayImage == 67)
does not give answer

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Answer by As Has on 11 Sep 2018
Edited by Walter Roberson
on 11 Sep 2018

i=imresize(i,[256 256]);
a=64; b=64; %window size
x=size(i,1)/a; y=size(i,2)/b;
m=a*ones(1,x); n=b*ones(1,y);
C =mat2cell(i,m,n);
C = C(:);
%# display tiles i subplots
for j=1:a*b
block_image = mean2(C{j});
if block_image > 10
imshow( C{j} )


what is the n variable?
Your code is very useful for me, but I wonder, if I can display only the block with maximum mean value, what will I do? Please answer me.
Image Analyst
on 30 Nov 2018
It is not necessary that you do ONLY that. You can do whatever you want. You can keep track of the means for all block and display only the single block that has the highest mean if you want. See my attached blockproc demos.

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