matlab - How to rearrange matrix column into block using for loop? -

i working on project have used image size (512x512)then have divided whole image 8 there 64x64 block have rearranged each 8x8 image patch single column , new size 64x4069. want original size i.e 512x512,please me how using loop instead of 'col2im'

a=imread('lena.png'); b=double(a); [m,n] = size(b); bl=8; br=m/bl; bc=n/bl; out = zeros(size(reshape(b,bl*bl,[]))); count = 1; = 1:br     j= 1:bc         block = b((j-1)*bl + 1:(j-1)*bl + bl, (i-1)*bl + 1:(i-1)*bl + bl);         out(:,count) = block(:);         count = count + 1;     end end 

this script written backwards. assumptions have made, because not every rectangular matrix can arise process described, , because dimensions of original matrix cannot uniquely determined set of blocks. so, assume original matrix square one, , blocks squares well.

by way, in code use j in formula row indices , columns; assumed mistake, , amended below.

out = kron((0:3)', 1:16);   % testing; have 64x4096 matrix here [m,n] = size(out); osize = sqrt(n*m);  bl = sqrt(m); br = osize/bl; bc = br; original = zeros(osize); count = 1; = 1:br     j = 1:bc         block = zeros(bl);         block(:) = out(:,count);         original(1+(i-1)*bl : i*bl, 1+(j-1)*bl : j*bl) = block;         count = count + 1;     end end 

input testing:

 0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0  1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16  2     4     6     8    10    12    14    16    18    20    22    24    26    28    30    32  3     6     9    12    15    18    21    24    27    30    33    36    39    42    45    48 

output:

 0     2     0     4     0     6     0     8  1     3     2     6     3     9     4    12  0    10     0    12     0    14     0    16  5    15     6    18     7    21     8    24  0    18     0    20     0    22     0    24  9    27    10    30    11    33    12    36  0    26     0    28     0    30     0    32 13    39    14    42    15    45    16    48