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% [PYR, INDICES] = buildLpyr(IM, HEIGHT, FILT1, FILT2, EDGES)
%
% Construct a Laplacian pyramid on matrix (or vector) IM.
%
% HEIGHT (optional) specifies the number of pyramid levels to build. Default
% is 1+maxPyrHt(size(IM),size(FILT)). You can also specify 'auto' to
% use this value.
%
% FILT1 (optional) can be a string naming a standard filter (see
% namedFilter), or a vector which will be used for (separable)
% convolution. Default = 'binom5'. FILT2 specifies the "expansion"
% filter (default = filt1). 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.
function [pyr,pind] = buildLpyr(im, ht, filt1, filt2, edges)
if (nargin < 1)
error('First argument (IM) is required');
end
im_sz = size(im);
%------------------------------------------------------------
%% OPTIONAL ARGS:
if (exist('filt1') ~= 1)
filt1 = 'binom5';
end
if isstr(filt1)
filt1 = namedFilter(filt1);
end
if ( (size(filt1,1) > 1) & (size(filt1,2) > 1) )
error('FILT1 should be a 1D filter (i.e., a vector)');
else
filt1 = filt1(:);
end
if (exist('filt2') ~= 1)
filt2 = filt1;
end
if isstr(filt2)
filt2 = namedFilter(filt2);
end
if ( (size(filt2,1) > 1) & (size(filt2,2) > 1) )
error('FILT2 should be a 1D filter (i.e., a vector)');
else
filt2 = filt2(:);
end
max_ht = 1 + maxPyrHt(im_sz, max(size(filt1,1), size(filt2,1)));
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 (exist('edges') ~= 1)
edges= 'reflect1';
end
%------------------------------------------------------------
if (ht <= 1)
pyr = im(:);
pind = im_sz;
else
if (im_sz(2) == 1)
lo2 = corrDn(im, filt1, edges, [2 1], [1 1]);
elseif (im_sz(1) == 1)
lo2 = corrDn(im, filt1', edges, [1 2], [1 1]);
else
lo = corrDn(im, filt1', edges, [1 2], [1 1]);
int_sz = size(lo);
lo2 = corrDn(lo, filt1, edges, [2 1], [1 1]);
end
[npyr,nind] = buildLpyr(lo2, ht-1, filt1, filt2, edges);
if (im_sz(1) == 1)
hi2 = upConv(lo2, filt2', edges, [1 2], [1 1], im_sz);
elseif (im_sz(2) == 1)
hi2 = upConv(lo2, filt2, edges, [2 1], [1 1], im_sz);
else
hi = upConv(lo2, filt2, edges, [2 1], [1 1], int_sz);
hi2 = upConv(hi, filt2', edges, [1 2], [1 1], im_sz);
end
hi2 = im - hi2;
pyr = [hi2(:); npyr];
pind = [im_sz; nind];
end