Scilab Wavelet Toolbox Function
Last update : Feburary 2006
appcoef2 - approximation coefficient extraction for two
dimensional multiple stride fast discrete wavelet decompostion
Calling Sequence
-
ac=appcoef2(c,s,wavename,level,[extension_method])
Parameters
-
c
: Coefficient Bunch Vector
-
s
: Coefficient Size Matrix
-
wavename
: wavelet name
- 'haar': haar wavelet
- 'db1': daubechies 1 wavelet, same with haar
- 'db2': daubechies 2 wavelet
- 'db3': daubechies 3 wavelet
- 'db4': daubechies 4 wavelet
- 'db5': daubechies 5 wavelet
- 'db6': daubechies 6 wavelet
- 'db7': daubechies 7 wavelet
- 'db8': daubechies 8 wavelet
- 'db9': daubechies 9 wavelet
- 'db10': daubechies 10 wavelet
-
level
: Decompostion Level of the coefficient you want
-
extension_method
: Signal Extension Method, default is 'symh'
- 'zpd': zero padding method
- 'ppd': period extension method
- 'asymh': half asymmetric extension method
- 'asymw': whold asymmetric extension method
- 'symh': half symmetric extension method
- 'symw': whole symmetric extension method
- 'sp0': border value constant extension method
- 'sp1': border value linear extension method
-
ac
: Approximation Coefficient
Description
This function extracts approximation coefficent from
coefficent bunch vector. Almost all level approximation
coefficients are obtained from inverse wavelet transform. So the
wavelet name and extension method should be presented, consistently
with those of the decomposition procedure. Only the highest
decomposed approximation coefficent does not need inverse transform.
Examples
-->img=rand(64,64);
-->[c,s]=wavedec2(img,3,'db2','sp0');
-->a1=appcoef2(c,s,'db2',1,'sp0');
-->size(a1)
ans =
! 33. 33. !
-->a2=appcoef2(c,s,'db2',2,'sp0');
-->size(a2)
ans =
! 18. 18. !
-->a3=appcoef2(c,s,'db2',3,'sp0');
-->size(a3)
ans =
! 10. 10. !
See Also
appcoef
,
detcoef
,
wrcoef
,
detcoef2
,
wrcoef2