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Pit Pattern Classification in Colonoscopy using Wavelets - WaveLab

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2 <strong>Wavelets</strong><br />

Logarithm of energy (LogEnergy)<br />

cost(I) =<br />

N∑<br />

log ∗ (s) with s = I(i) 2<br />

i=1<br />

Entropy<br />

N∑<br />

cost(I) = − s log ∗ (s) with s = I(i) 2<br />

i=1<br />

L p -Norm<br />

cost(I) =<br />

N∑<br />

|I(i)| p<br />

i=1<br />

Threshold<br />

cost(I) =<br />

N∑<br />

{ 1 if I(i) > t<br />

a with a =<br />

0 else<br />

i=1<br />

where I is the <strong>in</strong>put sequence (the subband), N is the length of the <strong>in</strong>put, log ∗ is the logfunction<br />

with the convention log(0) = 0 and t is some threshold value.<br />

(a) Source image<br />

(b) LogEnergy (c) Entropy (d) L-Norm (e) Threshold<br />

Figure 2.3: Different decomposition trees result<strong>in</strong>g from different cost functions us<strong>in</strong>g the<br />

Haar wavelet.<br />

16

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