how to divide a grayscale image into 8*8 blocks and return it from my function?

i do have a code, but it doesn't work quickly for 8*8. works perfectly for 32 and higher block sizes. it doesn't return the blocks either.

function y=segment1(f)
rgbImage = f;
imshow(rgbImage);
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
drawnow;
[rows columns numberOfColorBands] = size(rgbImage);
blockSizeR =8;
blockSizeC =8;
wholeBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, wholeBlockRows), rem(rows, blockSizeR)];
wholeBlockCols = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, wholeBlockCols), rem(columns, blockSizeC)];
if numberOfColorBands > 1
  ca = mat2cell(rgbImage, blockVectorR, blockVectorC, numberOfColorBands);
else
  ca = mat2cell(rgbImage, blockVectorR, blockVectorC);
end
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);
    subplot(numPlotsR, numPlotsC, plotIndex);
    rgbBlock=ca{r,c};
    imshow(rgbBlock);
    [rowsB columnsB numberOfColorBandsB] = size(rgbBlock);
    caption = sprintf('Block #%d of %d\n%d rows by %d columns', plotIndex, numPlotsR*numPlotsC, rowsB, columnsB);
    
    drawnow;
    plotIndex = plotIndex + 1;
  end
end

end

Answer 1

[Walter Roberson]

Your code starts

function y=segment1(f)

so it will return whatever is stored in the variable "y" by the function. But you do not store anything into y, so it cannot return the blocks. You need to store the blocks in y.

[chaitanya g p]

yes. great. thanks. but any suggestions to speed it up?

[Walter Roberson]

No, other than the trivial that you do not need to generate caption since you do not use it. Plotting a lot of different subplots is not fast, so avoid doing it.

It might be the case that montage suits your needs.

Be sure to credit Image Analyst in your comments, for the use of his code; see http://www.mathworks.com/matlabcentral/answers/34755-image-division#answer_43594

[chaitanya g p]

hey. regarding the storing of value in y. how do i do that? please help me out.

[Walter Roberson]

What is your defined output type? What kind of variable do you need to return? What is it that needs to be returned?