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wdcbm2

Thresholds for wavelet 2-D using Birge-Massart strategy

Syntax

Description

[THR,NKEEP] = wdcbm2(C,S,ALPHA,M) returns level-dependent thresholds THR and numbers of coefficients to be kept NKEEP, for de-noising or compression. THR is obtained using a wavelet coefficients selection rule based on the Birge-Massart strategy.

[C,S] is the wavelet decomposition structure of the image to be de-noised or compressed, at level j = size(S,1)-2.

ALPHA and M must be real numbers greater than 1.

THR is a matrix 3 by j, THR(:,i) contains the level dependent thresholds in the three orientations: horizontal, diagonal, and vertical, for level i.

NKEEP is a vector of length j, NKEEP(i) contains the number of coefficients to be kept at level i.

j, M and ALPHA define the strategy:

Typically ALPHA = 1.5 for compression and ALPHA = 3 for de-noising.

A default value for M is M = prod(S(1,:)), the length of the coarsest approximation coefficients, since the previous formula leads for i = j+1, to nj+1 = M = prod(S(1,:)).

Recommended values for M are from prod(S(1,:)) to 6*prod(S(1,:)).

wdcbm2(C,S,ALPHA) is equivalent to wdcbm2(C,S,ALPHA,prod(S(1,:))).

Examples

See Also
wdencmp, wpdencmp

References

Birgé, L.; P. Massart (1997). "From model selection to adaptive estimation," in D. Pollard (ed), Festchrift for L. Le Cam, Springer, pp. 55-88.


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