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.TH "WT2Dext" 2 " 01 June 1997" "Fractales Group" "Scilab Function"
.so ../sci.an
.SH NAME
WT2Dext - Extract a Projection from a 2D WT
.sp
Author: Bertrand Guiheneuf
.sp
This routine extracts a projection from the wavelet transform of a 2D matrix.
.sp
.sp
.SH Usage
\f(CR[\fPV\f(CR]\fP=WT2Dext(wt, Scale, Num)
.SH Input parameter
.RS
.TP
o
\fBwt\fP : real unidimensional matrix \f(CR[\fPm,n\f(CR]\fP
Contains the wavelet transform (obtained with FWT2D).
.TP
o
\fBw Scale\fP : real scalar
Contains the scale level of the projection to extract.
.TP
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\fBw Num\fP : real scalar
Contains the number of the output to extract in level \fIScale\fP (between 1 and 4)
.RE
.SH Output parameter
.RS
.TP
o
\fBV\fP : real matrix \f(CR[\fPm,n\f(CR]\fP
Contains the matrix to be visualized directly
.RE
.SH Description
.SH Introduction
At each scale, a wavelet transform contains 4 outputs (HL, HH, LH and HH at the last scale). This routine is used to extract a particular component at a desired scale.
.SH Parameters
\fIwt\fP must be a real matrix. It's generally obtained with FWT2D. It contains the wavelet transform coefficients.
\fINum\fP is 1,2,3, or 4 (at the last scale). Each number coresponds to a particular 2D frequency component.
.RS
.TP
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1 : HL
High frequency in row direction, Low in column direction.
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2 : HH
High frequency in row direction, High in column direction.
.TP
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3 : LH
Low frequency in row direction, High in column direction.
.TP
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4 : LL
Low frequency in row direction, Low in column direction.
Only for the last scale (equals 0 for the other scales).
.RE
\fIV\fP the wavelet coefficents at scale \fIScale\fP with fequency component given by \fINum\fP
.SH Example
a=rand(256,256);
q=MakeQMF('daubechies',4);
wt = FWT2D(a,8,q);
V=WT2Dext(wt,2,2);
viewmat(V);
.SH See Also
FWT2D, IWT2D, WT2DVisu,
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