how do i divide an image into blocks?

I have this image (2848 x 4288) and i want to divide it into 9 blocks and perform some operations on individual or each block. For example i perform this operations on an image:;

y = rgb2gray(imresize(imread('DSC_0009.jpg'),.2)); 
z = 255.0 - 1.0 * double(y);
 z = z ./5 ;
 z2 = imfilter(z, fspecial('average', 15));
 z2(z2 > 35) = 35;
 z2(z2 < 30) = 0;
 surface(z2);
 shading interp;
 axis ij;
 axis tight;

I want to do a similar operation on each of the blocks and output it as well.

thank you.

[Rena Berman]

(Answers dev) Restored question.

Answer 1

[Image Analyst]

See the FAQ for code to perform it two different ways, normal indexing, and the cell2mat() function: http://matlab.wikia.com/wiki/FAQ#How_do_I_split_an_image_into_non-overlapping_blocks.3F

Answer 2

[Image Analyst]

You can also use blockproc() if you don't need to store the subimages but just need to perform some operation on them and give you an output image. See attached demos for a variety of ways to use blockproc().

[Rey Kelvin Peralta]

How do i perform operations on individual blocks? I have this code:

function test_block

      % Function that is used to process each block
      function z2 = process_block(x)
          y = x.data; % Get the block itself

          % Apply the operations
          z = 255.0 - 1.0 * double(y); 
          z = z ./5 ; 

          z2 = imfilter(z, fspecial('average', 15)); 
          z2(z2 > 35) = 35; 
          z2(z2 < 30) = 0;
       end

% Specify total number of blocks per row and column
num_blocks_row = 3;
num_blocks_col = 3;

% Read in image
img = rgb2gray(imread('DSC_0009.jpg')); 

% Determine how large each block should be
block_size = floor([size(img,1)/num_blocks_row size(img,2)/num_blocks_col]);

% Perform processing of each block
out = blockproc(img, block_size, @process_block);

% Show the results
surface(out); 
shading interp; axis ij; axis tight;

end

but this cant access individual blocks and perform filtering and thresholding with different values/threshold values.

Thank you.

[Image Analyst]

Follow the example of blockproc_demo2 where I use myFilter. You can put whatever code you want into that function, such as the code you showed above.

[Rey Kelvin Peralta]

Also sir, is there a way we can export my code or the figure/surface/3dsurface of this code in to a format into which blender can read it? please help

[Image Analyst]

I don't know. I've never used blender. However using fwrite() or fprintf() you can create any file you want.

[Walter Roberson]

http://www.mathworks.com/matlabcentral/fileexchange/42816-numsim-toolbox/content/NumSim/Documentation/html/UserGuide_Blender.html

http://www.mathworks.com/matlabcentral/fileexchange/27982-wavefront-obj-toolbox

http://www.mathworks.com/matlabcentral/fileexchange/43640-export-voxel-data