wavelets

Question

aavula 2011-9-9

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https://ww2.mathworks.cn/matlabcentral/answers/15509-wavelets

采纳的回答： Wayne King

difference b/w the functions dwt2 and wavedec2

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Answer 1

Wayne King 2011-9-9

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Hi Aavula, dwt2 gives you the 2D (separable) discrete wavelet transform at one level.

wavedec2 gives you the 2D (separable) discrete wavelet transform at a number of levels if you wish (provided as an input argument). wavedec2 uses dwt2 to iterate on the LL component.

Hope that helps,

Wayne

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aavula 2011-9-10

thanks...how to get the coefficients(approx and detail)separately

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Answer 2

Wayne King 2011-9-10

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From wavedec2 you obtain a C and S vector. You can then use detcoef2 and appcoef2 to extract the detail and approximation coefficients at a given level.

For example:

image = randn(16,16);
[C,S] = wavedec2(image,3,'db2');
% get level 2 detail coefficients
[H,V,D] = detcoef2('all',C,S,2);
% get level 2 approx. coefficients
A = appcoef2(C,S,'db2',2);