Can anyone please explain waveletTransform coding

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gobika ranthil
gobika ranthil 2016-11-3
回答： anita jasmine 2020-10-24
I have a code for waveletTransform to find the feature vector containing the first 2 moments of wavelet coefficients.Can anybody please explain me this code?I don't understand what is coif1 and coeff_1 in this code.
function wavelet = waveletTransform(image)
% input: image to process and extract wavelet coefficients from
% output: 1x20 feature vector containing the first 2 moments of wavelet
% coefficients
imgGray = double(rgb2gray(image))/255;
imgGray = imresize(imgGray, [256 256]);
coeff_1 = dwt2(imgGray', 'coif1');
coeff_2 = dwt2(coeff_1, 'coif1');
coeff_3 = dwt2(coeff_2, 'coif1');
coeff_4 = dwt2(coeff_3, 'coif1');
% construct the feaute vector
meanCoeff = mean(coeff_4);
stdCoeff = std(coeff_4);
wavelet = [meanCoeff stdCoeff];
end

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回答（1 个）

anita jasmine
anita jasmine 2020-10-24
Coiflet is derived from daubechies wavelet.
  1. the coiflet wavelet of order 1 is computed for image.
coeff_1 = dwt2(imgGray', 'coif1');
2. Applying 4 levels of 2DWT
coeff_2 = dwt2(coeff_1, 'coif1');
coeff_3 = dwt2(coeff_2, 'coif1');
coeff_4 = dwt2(coeff_3, 'coif1');
3.computing the first 2 moments mean and std

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