Use of wcodemat and wkeep ?
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sz=size(input image);
LL3 = wcodemat(a3,ncolors,'m',X); LL3 = wkeep(LL3, sz/8);
HL3 = wcodemat(h3,ncolors,'m',X); HL3 = wkeep(HL3, sz/8);
LH3 = wcodemat(v3,ncolors,'m',X); LH3 = wkeep(LH3, sz/8);
HH3 = wcodemat(d3,ncolors,'m',X); HH3 = wkeep(HH3, sz/8);
By using wkeep will my input image's information be lost?
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Accepted Answer
Wayne King
on 8 Aug 2013
That isn't the use case for wcodemat(). wcodemat() is simply for scaling images for display purposes.
The 2D DWT is invertible. The only loss is numerical precision unless of course you modify the wavelet coefficients, which is often the purpose of doing the wavelet transform in the first place. If you don't modify the coefficients, then the transform is invertible (just the the DFT)
load nbarb1;
[C,S] = wavedec2(X,3,'db4');
Xrec = waverec2(C,S,'db4');
max(max(abs(X-Xrec)))
wkeep() and wkeep2() -- wkeep2 is for image data. It is a convenience function that is used internally in other functions of the Wavelet Toolbox to retain the appropriate output from convolutions. An example is the use of wkeep2() inside of iswt2.m
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More Answers (1)
Wayne King
on 8 Aug 2013
Edited: Wayne King
on 8 Aug 2013
Yes, in the sense that the inverse wavelet transform will no longer work. By using wkeep() you are removing elements of the detail images.
The same is true of using wcodemat() which is really just for display.
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