| A wavelet question [message #81034] |
Wed, 01 August 2012 14:19 |
Konstantinos
Messages: 29
Registered: April 2011
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Junior Member |
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Suppose that i want to use the biorthogonial wavelet filter that used for Jpeg2000 decomposition (Cohen-Daubechies 9/7 wavelet filter).
Let suppose that i do not want to write my own code or use available codes from internet AND i want to Use the IDL WV_WDT function.
But if i want to use WV_WDT i must first create, lets say, a WV_FN_jp2k function that describes my wavelet.
There are 2 ways to implement the wavelet transform Lifting and Convolution. I think that ILD uses the convolution method. (AM I CORRECT???)
According to IDL wavelet manual "The wavelet consists of two components, the scaling function which describes the low-pass filter for the wavelet transform, and the wavelet function which describes the band-pass filter for the transform."
So if i got it right I have to define the low pass and the band pass filter coefficients, in my WV_FN_jp2k.
So it must look like this.
FUNCTION wv_fn_j2k, Order, Scaling, Wavelet, Ioff, Joff
;Definition of Low Pass (scaling) and High pass (wavelet) Filter
; values from http://en.wikipedia.org/wiki/Cohen-Daubechies-Feauveau_wavel et
scaling= [0.026748757411d , $
-0.016864118443d, $
0.078223266529d , $
0.266864118443d , $
0.602949018236d , $
0.266864118443d , $
-0.078223266529d, $
-0.016864118443d, $
0.026748757411d ]
wavelet= [0d, 0.091271763114d , $
-0.057543526229d , $
-0.591271763114d , $
1.11508705d , $
-0.591271763114d , $
-0.057543526229d , $
0.091271763114d , 0]
order_range = [1,1,1]
order = order_range[2]
n = N_ELEMENTS(scaling)
ioff = -n/2 + 2 ; offset for scaling
joff = ioff
info = {family:'j2k', $
order_name:'Order', $
order_range:[1,1,1], $
order:1, $
discrete:1, $
orthogonal:0, $
symmetric:1, $
support:1, $
moments:4, $
regularity:0.0}
RETURN, info
END
COULD BE CORRECT or i am missing something??
Thank u in advance 4 your answers
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