could you fix these codes?

Tia
2013 5 14
3 个回答
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0 个投票

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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Jan
Jan 2013-5-14
编辑：Jan 2013-5-14

1 个投票

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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Tia
Tia 2013-5-16
wow..it's great.it's more efficient. thank you
Image Analyst
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
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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Iman Ansari
Iman Ansari 2013-5-14
编辑：Iman Ansari 2013-5-14

0 个投票

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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Tia
Tia 2013-5-14
编辑：Tia 2013-5-14
i'm still confused. actually if i have these codes:
I=imread('filename');
ul=I(1:256,1:256);
ur=I(1:256,257:512);
ll=I(257:512,1:256);
lr=I(257:512,257:512);
s=[ul,lr;ur,lr];
figure,imshow(s)
but if i have 32x32pixels,then i divide it into 8x8blocks.i should to write long codes
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);
s=[a1,b1,c2,d3;a3,b2,c3,d4;...]
i want to use 'for'. how can i get it? thanks for your fast answer
Iman Ansari
Iman Ansari 2013-5-14
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
Tia 2013-5-16
thank you

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David Sanchez
David Sanchez 2013-5-14

0 个投票

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

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