# how to generate location of matrix?

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Tia on 22 Mar 2013
1.how to generate location (1,1) of matrix 2. For example, we may have a 512x512 pixel image, on which we impose a grid of 512x512 threads that are subdivided into thread blocks with 8x8 threads each, for a total of 64x64 thread blocks. how to generate location (1,1) of matrix on each block 8x8 for 64x64thread blocks?i would like to get location (1,1) on each block 8x8 then multiply with 0-255.
thanks
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Tia on 22 Mar 2013
Edited: Andrei Bobrov on 22 Mar 2013
I=double(imread('lena.jpg'));
T=dctmtx(8);
dct2 = @(a) T * a.data * T';
[mI,nI]=size(I);
mb=mI/8;nb=nI/8;
x=randi([0,255],8,8);
dc=mean2(I);
m=x.*dc;
B = blockproc(I,[8 8],dct2);
B2 = blockproc(B,[8 8],@(a) m .* a.data);
idct2 = @(a) T' * a.data * T;
I2 = blockproc(B2,[8 8],idct2);
imshow(I), figure, imshow(I2)
i want to change value on dc (DCT coefficient) from 0 to 255. how to write it? when i run it, B2 can't be operate. actually, i want to generate location (1,1) of matrix from that image. thank you

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### Accepted Answer

Walter Roberson on 22 Mar 2013
B2(1:64:end, 1:64:end) = 255;
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