dwt2dir.m

用MATLAB编写的人脸检测算法

function [a,h] = dwt2dir(x,varargin)
%DWT2 Single-level discrete 2-D wavelet transform.
%   DWT2 performs a single-level 2-D wavelet decomposition
%   with respect to either a particular wavelet ('wname',
%   see WFILTERS for more information) or particular wavelet filters
%   (Lo_D and Hi_D) you specify.
%
%   [CA,CH,CV,CD] = DWT2(X,'wname') computes the approximation
%   coefficients matrix CA and details coefficients matrices 
%   CH, CV, CD, obtained by a wavelet decomposition of the 
%   input matrix X.
%   'wname' is a string containing the wavelet name.
%
%   [CA,CH,CV,CD] = DWT2(X,Lo_D,Hi_D) computes the 2-D wavelet
%   decomposition as above given these filters as input:
%   Lo_D is the decomposition low-pass filter.
%   Hi_D is the decomposition high-pass filter.
%   Lo_D and Hi_D must be the same length.
%
%   Let SX = size(X) and LF = the length of filters; then
%   size(CA) = size(CH) = size(CV) = size(CD) = SA where
%   SA = CEIL(SX/2), if the DWT extension mode is set to
%   periodization. SA = FLOOR((SX+LF-1)/2) for the other
%   extension modes. For the different DWT extension modes, 
%   see DWTMODE.
%
%   [CA,CH,CV,CD] = DWT2(...,'mode',MODE) computes the wavelet 
%   decomposition with the extension mode MODE you specify.
%   MODE is a string containing the extension mode.
%   Example: 
%     [ca,ch,cv,cd] = dwt2(x,'db1','mode','sym');
%
%   See also DWTMODE, IDWT2, WAVEDEC2, WAVEINFO.

%   M. Misiti, Y. Misiti, G. Oppenheim, J.M. Poggi 12-Mar-96.
%   Last Revision: 02-Aug-2000.
%   Copyright 1995-2002 The MathWorks, Inc.
% $Revision: 1.15 $