How do I divide an image into blocks for processing?

I am new to MATLAB.

I am trying to write code which will divide the image in nonoverlaping blocks of size 3*3. I am supposed to do operations on specific blocks like getting the value of the center pixel of block and do some operations.

I don't know where to start. Using command like blockproc wont help. Can anyone suggest a start point?

[Jiro Doke]

Why won't using "blockproc" help? That's exactly for doing what you proposed.

[Brett Shoelson]

What Jiro said.

[David Young]

Agreed - blockproc should be the business.

[Aparna RAJAWAT]

I want to divide an image into different block size.and image size is 16x16.block size are 4x4,5x5 and so on.please help me how to do coding in matlab

[Image Analyst]

Aparna, please see the FAQ

Answer 1

[Yaw]

The best way to do this is to use the "mat2cell" command. It's very simple.

1. a=3; b=3; %window size
2. x=size(f,1)/a; y=size(f,2)/b; %f is the original image
3. m=a*ones(1,x); n=b*ones(1,y);
4. I=mat2cell(f,m,n);

[Walter Roberson]

blockproc() is able to handle situations where the original matrix does not happen to have dimensions that are multiples of 3. Your code will crash on those cases.

Answer 2

[Vieniava]

Suppose I is your image matrix. Trivial way is shown below:

s=size(I);
wing=1;         % ;)
bs=2*wing+1;      % block size

for i=wing: bs : (s(1)-wing)
  for j=wing : bs : (s(2)-wing)

       BLOCK=I( (i-wing):(i+wing) , (j-wing):(j+wing) );
       %
       % paste your function/code  which processes the BLOCK
       %
    end
  end