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executable file 70 lines (52 sloc) 2.016 kB
% RESDFT = reconSFpyrLevs(PYR,INDICES,LOGRAD,XRCOS,YRCOS,ANGLE,NBANDS,LEVS,BANDS)
%
% Recursive function for reconstructing levels of a steerable pyramid
% representation. This is called by reconSFpyr, and is not usually
% called directly.
% Eero Simoncelli, 5/97.
function resdft = reconSFpyrLevs(pyr,pind,log_rad,Xrcos,Yrcos,angle,nbands,levs,bands);
lo_ind = nbands+1;
dims = pind(1,:);
ctr = ceil((dims+0.5)/2);
% log_rad = log_rad + 1;
Xrcos = Xrcos - log2(2); % shift origin of lut by 1 octave.
if any(levs > 1)
lodims = ceil((dims-0.5)/2);
loctr = ceil((lodims+0.5)/2);
lostart = ctr-loctr+1;
loend = lostart+lodims-1;
nlog_rad = log_rad(lostart(1):loend(1),lostart(2):loend(2));
nangle = angle(lostart(1):loend(1),lostart(2):loend(2));
if (size(pind,1) > lo_ind)
nresdft = reconSFpyrLevs( pyr(1+sum(prod(pind(1:lo_ind-1,:)')):size(pyr,1)),...
pind(lo_ind:size(pind,1),:), ...
nlog_rad, Xrcos, Yrcos, nangle, nbands,levs-1, bands);
else
nresdft = fftshift(fft2(pyrBand(pyr,pind,lo_ind)));
end
YIrcos = sqrt(abs(1.0 - Yrcos.^2));
lomask = pointOp(nlog_rad, YIrcos, Xrcos(1), Xrcos(2)-Xrcos(1), 0);
resdft = zeros(dims);
resdft(lostart(1):loend(1),lostart(2):loend(2)) = nresdft .* lomask;
else
resdft = zeros(dims);
end
if any(levs == 1)
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)) )
const = (2^(2*order))*(factorial(order)^2)/(nbands*factorial(2*order));
Ycosn = sqrt(const) * (cos(Xcosn)).^order;
himask = pointOp(log_rad, Yrcos, Xrcos(1), Xrcos(2)-Xrcos(1),0);
ind = 1;
for b = 1:nbands
if any(bands == b)
anglemask = pointOp(angle,Ycosn,Xcosn(1)+pi*(b-1)/nbands,Xcosn(2)-Xcosn(1));
band = reshape(pyr(ind:ind+prod(dims)-1), dims(1), dims(2));
banddft = fftshift(fft2(band));
resdft = resdft + (sqrt(-1))^(nbands-1) * banddft.*anglemask.*himask;
end
ind = ind + prod(dims);
end
end
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