could you fix these codes?

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Tia 2013-5-14

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    I=imread('filename'); 
    a1=I(1:8,1:8);
    a2=I(1:8,9:16);
    a3=I(1:8,17:24);
    a4=I(1:8,25:32);
    b1=I(9:16,1:8);
    b2=I(9:16,9:16);
    b3=I(9:16,17:24);
    b4=I(9:16,25:32);
c1=I(17:24,1:8);
c2=I(17:24,9:16);
c3=I(17:24,17:24);
c4=I(17:24,25:32);
d1=I(25:32,1:8);
d2=I(25:32,9:16);
d3=I(25:32,17:24);
d4=I(25:32,25:32);

could you tell me how to make it short? Thank you

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Answer 1

Jan 2013-5-14

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编辑：Jan 2013-5-14

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Don't do this.

Hiding the index in the name of a variable is a bad programming pattern. It is much more efficient to use indices as indices:

img = reshape(a(1:32, 1:32), 8, 4, 8, 4);
img = permute(img, [1,3,2,4]);

Now you have img(:, :, 1, 1) instead of a1.

This is much faster, needs less memory, and allows to expand the method for millions of tiles easily.

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Image Analyst 2013-5-16

You may not even need to do that. It's possible that you do not need to even store the tiles at all. Do you? Why do these tiles need to be stored rather than just operated on and thrown away (reused)? Just operate on one tile at a time if you can - why store forever?

Tia 2013-7-15

i try it. but it can't be back at 1D.. how do i get it? is it possible? or any ideas how to spilt it into 8x8pixels,but i want to manipulate each 8x8pixels,then store the tiles at all? thank you for your time

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Answer 2

Iman Ansari 2013-5-14

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编辑：Iman Ansari 2013-5-14

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Hi. Use cell array:

I=imread('moon.tif');
C=mat2cell(I(1:32,1:32),8*ones(1,4),8*ones(1,4));
imshow(C{5},'InitialMagnification','fit')

C{5} or C{1,2} is a2 in your code.

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Iman Ansari 2013-5-14

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It's not good having variable named a1,a2,..., see this:

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

I=imread('moon.tif');
C=mat2cell(I(1:32,1:32),8*ones(1,4),8*ones(1,4));
imshow(C{5},'InitialMagnification','fit')

C in this code is:

C={a1,a2,a3,a4;b1,b2,b3,b4;c1,c2,c3,c4;d1,d2,d3,d4}

and for s:

s=[C{1,1} C{2,1} C{3,2} C{4,3};C{1,3} C{2,2} C{3,3} C{4,4};...]

Tia 2013-5-16

thank you

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Answer 3

David Sanchez 2013-5-14

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You can try as well something like this

I=imread(your_32x32_image_name);
division = 8; % set according to yuor needs
L = size(I,1)/division;
subI = cell( L,L );
for row=1:L
    for col=1:L
        subI{row,col} = I( (row:row*division),(col:(col*division)) );
    end
end