easily sub dividing image into blocks

Question

mahesh chathuranga 2013-9-10

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https://ww2.mathworks.cn/matlabcentral/answers/86775-easily-sub-dividing-image-into-blocks

回答： Tejashree Ladhake 2013-11-29

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?

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Image Analyst 2013-9-12

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

mahesh chathuranga 2013-9-13

thank you

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Answer 1

Azzi Abdelmalek 2013-9-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/86775-easily-sub-dividing-image-into-blocks#answer_96305

编辑：Azzi Abdelmalek 2013-9-10

在 MATLAB Online 中打开

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)

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mahesh chathuranga 2013-9-12

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

Jan 2013-9-12

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

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Answer 2

Jan 2013-9-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/86775-easily-sub-dividing-image-into-blocks#answer_96307

编辑：Jan 2013-9-12

在 MATLAB Online 中打开

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