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

Question

chaitanya g p 2016-3-30

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/276092-how-to-divide-a-grayscale-image-into-8-8-blocks-and-return-it-from-my-function

评论： Walter Roberson 2016-4-5

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

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Answer 1

Walter Roberson 2016-3-30

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/276092-how-to-divide-a-grayscale-image-into-8-8-blocks-and-return-it-from-my-function#answer_215568

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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.