easily sub dividing image into blocks

this is my programme

[m n]=size(I);_(example image size is 256*256)_ c=mat2cell(I,[4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4],[4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4]); this is difficult and i want to sub divide the any image into (m/4)*(n/4) blocks.how can i do this easily?

[Jan]

This does not look like a valid Matlab program. Please format the code properly and post valid Matlab syntax.

[Image Analyst]

FYI: note the long arrays of 4's can be replaced by the shorter expression: 4*ones(1,m/4)

[mahesh chathuranga]

thank you

Answer 1

[Azzi Abdelmalek]

im=rand(256);
[n,m]=size(im);
p=4
aa=1:p:n
bb=1:p:m
[ii,jj]=ndgrid(aa,bb)
out=arrayfun(@(x,y) im(x:x+p-1,y:y+p-1),ii,jj,'un',0)

[mahesh chathuranga]

thank you very much

[mahesh chathuranga]

thank you very much. but sir i want to do this with mat2cellfunction

[Jan]

There is nothing magic in MAT2CELL. You can simply use a loop directly, see [EDITED] in my answer.

Answer 2

[Jan]

Img    = rand(768, 1024);
[m, n] = size(Img);
Blocks = permute(reshape(Img, [4, m/4, 4, n/4]), [1, 3, 2, 4]);

Now the block [x,y] can be accessed as

Block(:, :, x, y)

[EDITED] And to create a cell:

Img    = rand(768, 1024);
[m, n] = size(Img);
m4     = m / 4;
n4     = n / 4;
Blocks = permute(reshape(Img, [4, m4, 4, n4]), [1, 3, 2, 4]);
C = cell(m4, n4)
for in = 1:n4
  for im = 1:m4
     C{im, in} = Blocks(:, :, im, in);
  end
end

[Andrei Bobrov]

Hi Jan! Or:

C = reshape(num2cell(Blocks,[1 2]),m4,n4);

[mahesh chathuranga]

thanks

[Alessandro Masullo]

This is the smartest solution that I've ever seen.

It's just pure beauty. Fantastic, I love it!

Answer 3

[Tejashree Ladhake]

yes, it works! thank you