Question about significancy of wavelet coefficients

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snake eyes 2011-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/14087-question-about-significancy-of-wavelet-coefficients

I'm doing watermarking project based on discrete wavelet transform. According to various research paper i understand that, the watermark should be embedded into highest wavelet coefficients. Now consider some wavelet coefficients: 12, -23 ,34 ,-123,56 Can anybody tell me which are the three highest coefficients?

Thanks in advance.

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Answer 1

the cyclist 2011-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/14087-question-about-significancy-of-wavelet-coefficients#answer_19311

在 MATLAB Online 中打开

Does this do what you want?

coefficients = [12,-23,34,-123, 56];
sortedCoefficients = sort(coefficients,'descend');
topThree = sortedCoefficients(1:3)

If you need the three highest by magnitude (e.g. -123 is the largest), then it's just a bit trickier:

coefficients = [12,-23,34,-123, 56];
[sortedCoefficients,sortingIndex] = sort(abs(coefficients),'descend');
topThree = sign(coefficients(sortingIndex(1:3))).*sortedCoefficients(1:3)