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Asked by Bhavini
on 17 Jun 2013

Hi all,

I have a binary image (with values 0 & 1) of the dimensions 497*597. I want to calculate the fraction (%) of pixels with value 1 in each array of 3*3 pixels out of the full image. can anybody help me in this regard?

Any help is highly appriciated.

Thanks in advance

Bhavini

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Answer by Andrei Bobrov
on 17 Jun 2013

Edited by Andrei Bobrov
on 17 Jun 2013

a = randi([0 1],497,597); ones_frac = conv2(a,ones(3),'valid')/9*100;

or if you have `Image Processing Toolbox`

ones_frac = blockproc(a,[3 3],@(x)sum(x.data(:))/9*100);

Answer by Bhomik Luthra
on 17 Jun 2013

Lets take a random matrix of size 497*597. I have found the number of 1's in each 3*3 matrix in first horizontal row, u can do it for 497/3 rows by putting a for loop.

a = randint(497,597);

for i = 1:597/3

p(i)= length(find (a(1:3,3*i-2:3*i)==1)) end

p(i) returns the number of 1's in each 3*3 matrix.

Bhomik Luthra

## 2 Comments

## Jan Simon

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/79257#comment_155302

Do you mean overlapping blocks, such that the first one goes from 1 to 3, the 2nd one from 2 to 4? Or should the block be mutually distinct?

## Bhavini

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/79257#comment_155304

Dear Jan,

Yes the blocks must be overlapping, starting from 1 upto 595 horizontally and 1 to 495 vertically.