help with dwt
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Alma o.a
le 15 Fév 2012
Modifié(e) : Azzi Abdelmalek
le 17 Oct 2013
hello everyone i'm doing a project on image watermarking. According to my algorithm i've to select sub-blocks from LH and HL sub-bands of an image. Is this possible? I have a 512*512 grayscale image and need to select 64*64 sub-blocks from the LH and HL sub-bands of the image. thanks in advance!
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Wayne King
le 16 Fév 2012
Hi Alma, Yes you can. It is not clear from your question whether you want to select 64x64 blocks from the first level details, or whether you want to decompose the image until you get to level 3.
dwtmode('per');
load woman;
% level 1
[C,S] = wavedec2(X,3,'bior3.5');
[H,V,D] = detcoef2('all',C,S,1);
Now you can select blocks from H and V.
The vertical details are obtained by highpass filtering the rows followed by lowpass filtering the columns. (with downsampling)
The horizontal details are obtained by lowpass filtering the rows and highpass filtering the columns (with downsampling)
Or
[H,V,D] = detcoef2('all',C,S,3);
If you want them from level 3.
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