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% [PYR, INDICES] = buildWpyr(IM, HEIGHT, FILT, EDGES)
%
% Construct a separable orthonormal QMF/wavelet pyramid on matrix (or vector) IM.
%
% HEIGHT (optional) specifies the number of pyramid levels to build. Default
% is maxPyrHt(IM,FILT). You can also specify 'auto' to use this value.
%
% FILT (optional) can be a string naming a standard filter (see
% namedFilter), or a vector which will be used for (separable)
% convolution. Filter can be of even or odd length, but should be symmetric.
% Default = 'qmf9'. EDGES specifies edge-handling, and
% defaults to 'reflect1' (see corrDn).
%
% PYR is a vector containing the N pyramid subbands, ordered from fine
% to coarse. INDICES is an Nx2 matrix containing the sizes of
% each subband. This is compatible with the MatLab Wavelet toolbox.
% Eero Simoncelli, 6/96, based on original lisp code from 1987.
function [pyr,pind] = buildWpyr(im, ht, filt, edges)
if (nargin < 1)
error('First argument (IM) is required');
end
%------------------------------------------------------------
%% OPTIONAL ARGS:
if (exist('filt') ~= 1)
filt = 'qmf9';
end
if (exist('edges') ~= 1)
edges= 'reflect1';
end
if isstr(filt)
filt = namedFilter(filt);
end
if ( (size(filt,1) > 1) & (size(filt,2) > 1) )
error('FILT should be a 1D filter (i.e., a vector)');
else
filt = filt(:);
end
hfilt = modulateFlip(filt);
% Stagger sampling if filter is odd-length:
if (mod(size(filt,1),2) == 0)
stag = 2;
else
stag = 1;
end
im_sz = size(im);
max_ht = maxPyrHt(im_sz, size(filt,1));
if ( (exist('ht') ~= 1) | (ht == 'auto') )
ht = max_ht;
else
if (ht > max_ht)
error(sprintf('Cannot build pyramid higher than %d levels.',max_ht));
end
end
if (ht <= 0)
pyr = im(:);
pind = im_sz;
else
if (im_sz(2) == 1)
lolo = corrDn(im, filt, edges, [2 1], [stag 1]);
hihi = corrDn(im, hfilt, edges, [2 1], [2 1]);
elseif (im_sz(1) == 1)
lolo = corrDn(im, filt', edges, [1 2], [1 stag]);
hihi = corrDn(im, hfilt', edges, [1 2], [1 2]);
else
lo = corrDn(im, filt, edges, [2 1], [stag 1]);
hi = corrDn(im, hfilt, edges, [2 1], [2 1]);
lolo = corrDn(lo, filt', edges, [1 2], [1 stag]);
lohi = corrDn(hi, filt', edges, [1 2], [1 stag]); % horizontal
hilo = corrDn(lo, hfilt', edges, [1 2], [1 2]); % vertical
hihi = corrDn(hi, hfilt', edges, [1 2], [1 2]); % diagonal
end
[npyr,nind] = buildWpyr(lolo, ht-1, filt, edges);
if ((im_sz(1) == 1) | (im_sz(2) == 1))
pyr = [hihi(:); npyr];
pind = [size(hihi); nind];
else
pyr = [lohi(:); hilo(:); hihi(:); npyr];
pind = [size(lohi); size(hilo); size(hihi); nind];
end
end