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% [PYR, INDICES] = buildSCFpyrLevs(LODFT, LOGRAD, XRCOS, YRCOS, ANGLE, HEIGHT, NBANDS)
%
% Recursive function for constructing levels of a steerable pyramid. This
% is called by buildSCFpyr, and is not usually called directly.
% Original code: Eero Simoncelli, 5/97.
% Modified by Javier Portilla to generate complex bands in 9/97.
function [pyr,pind] = buildSCFpyrLevs(lodft,log_rad,Xrcos,Yrcos,angle,ht,nbands);
if (ht <= 0)
lo0 = ifft2(ifftshift(lodft));
pyr = real(lo0(:));
pind = size(lo0);
else
bands = zeros(prod(size(lodft)), nbands);
bind = zeros(nbands,2);
% log_rad = log_rad + 1;
Xrcos = Xrcos - log2(2); % shift origin of lut by 1 octave.
lutsize = 1024;
Xcosn = pi*[-(2*lutsize+1):(lutsize+1)]/lutsize; % [-2*pi:pi]
order = nbands-1;
%% divide by sqrt(sum_(n=0)^(N-1) cos(pi*n/N)^(2(N-1)) )
%% Thanks to Patrick Teo for writing this out :)
const = (2^(2*order))*(factorial(order)^2)/(nbands*factorial(2*order));
%
% Ycosn = sqrt(const) * (cos(Xcosn)).^order;
%
% analityc version: only take one lobe
alfa= mod(pi+Xcosn,2*pi)-pi;
Ycosn = 2*sqrt(const) * (cos(Xcosn).^order) .* (abs(alfa)<pi/2);
himask = pointOp(log_rad, Yrcos, Xrcos(1), Xrcos(2)-Xrcos(1), 0);
for b = 1:nbands
anglemask = pointOp(angle, Ycosn, Xcosn(1)+pi*(b-1)/nbands, Xcosn(2)-Xcosn(1));
banddft = ((-i)^(nbands-1)) .* lodft .* anglemask .* himask;
band = ifft2(ifftshift(banddft));
% bands(:,b) = real(band(:));
% analytic version: full complex value
bands(:,b)=band(:);
bind(b,:) = size(band);
end
dims = size(lodft);
ctr = ceil((dims+0.5)/2);
lodims = ceil((dims-0.5)/2);
loctr = ceil((lodims+0.5)/2);
lostart = ctr-loctr+1;
loend = lostart+lodims-1;
log_rad = log_rad(lostart(1):loend(1),lostart(2):loend(2));
angle = angle(lostart(1):loend(1),lostart(2):loend(2));
lodft = lodft(lostart(1):loend(1),lostart(2):loend(2));
YIrcos = abs(sqrt(1.0 - Yrcos.^2));
lomask = pointOp(log_rad, YIrcos, Xrcos(1), Xrcos(2)-Xrcos(1), 0);
lodft = lomask .* lodft;
[npyr,nind] = buildSCFpyrLevs(lodft, log_rad, Xrcos, Yrcos, angle, ht-1, nbands);
pyr = [bands(:); npyr];
pind = [bind; nind];
end