help with dwt
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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!
1 个评论
the cyclist
2012-2-15
I suggest you give your question a more meaningful title.
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Wayne King
2012-2-16
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.
5 个评论
Alma o.a
2012-2-18
Wayne King
2012-2-18
Because as I wrote in my post, it was not clear to me when you said 64x64, whether you wanted the level 3 detail coefficients, or you simply wanted to select 64x64 blocks from the level 1 coefficients.
Since I was not sure, I went ahead and decomposed the image down to level 3 (no harm in doing that)
Alma o.a
2012-2-19
Alma o.a
2012-2-20
Wayne King
2012-2-20
Hi Alma, you want to use waverec2
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