this code divides an image into cell array. My question is these cell arrays are actually blocks or something else. If it is block, then how i combine all these blocks again to form the original image. Thanks for help.

% The first way to divide an image up into blocks is by using mat2cell().

blockSizeR = 150; % Rows in block.

blockSizeC = 100; % Columns in block.

% Figure out the size of each block in rows. 
% Most will be blockSizeR but there may be a remainder amount of less than that.

wholeBlockRows = floor(rows / blockSizeR);

blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)];

% Figure out the size of each block in columns. 

wholeBlockCols = floor(columns / blockSizeC);

blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)];

% Create the cell array, ca.  
% Each cell (except for the remainder cells at the end of the image)
% in the array contains a blockSizeR by blockSizeC by 3 color array.
% This line is where the image is actually divided up into blocks.

if numberOfColorBands > 1

  % It's a color image.
  ca = mat2cell(rgbImage, blockVectorR, blockVectorC, numberOfColorBands);

else
  ca = mat2cell(rgbImage, blockVectorR, blockVectorC);
end

% Now display all the blocks.

plotIndex = 1;

numPlotsR = size(ca, 1);

numPlotsC = size(ca, 2);

for r = 1 : numPlotsR

  for c = 1 : numPlotsC

    fprintf('plotindex = %d,   c=%d, r=%d\n', plotIndex, c, r);

    % Specify the location for display of the image.
    subplot(numPlotsR, numPlotsC, plotIndex);

    % Extract the numerical array out of the cell
    % just for tutorial purposes.
    rgbBlock = ca{r,c};

    imshow(rgbBlock); % Could call imshow(ca{r,c}) if you wanted to.
    [rowsB columnsB numberOfColorBandsB] = size(rgbBlock);

    % Make the caption the block number.

    caption = sprintf('Block #%d of %d\n%d rows by %d columns', ...
      plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);

    title(caption);

    drawnow;

    % Increment the subplot to the next location.

    plotIndex = plotIndex + 1;
  end
end

% Display the original image in the upper left.

subplot(4, 6, 1);

imshow(rgbImage);

title('Original Image');

Answer 1

[Walter Roberson]

The cell array will hold blocks. To convert the blocks back to an array use cell2mat()