reconSFpyr.m

% RES = reconSFpyr(PYR, INDICES, LEVS, BANDS, TWIDTH)
%
% Reconstruct image from its steerable pyramid representation, in the Fourier
% domain, as created by buildSFpyr.
%
% 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.
%
% LEVS (optional) should be a list of levels to include, or the string
% 'all' (default).  0 corresonds to the residual highpass subband.
% 1 corresponds to the finest oriented scale.  The lowpass band
% corresponds to number spyrHt(INDICES)+1.
%
% BANDS (optional) should be a list of bands to include, or the string
% 'all' (default).  1 = vertical, rest proceeding anti-clockwise.
%
% TWIDTH is the width of the transition region of the radial lowpass
% function, in octaves (default = 1, which gives a raised cosine for
% the bandpass filters).

%%% MODIFIED VERSION, 7/04, uses different lookup table for radial frequency!

% Eero Simoncelli, 5/97.

function res = reconSFpyr(pyr, pind, levs, bands, twidth)

%%------------------------------------------------------------
%% DEFAULTS:

if (exist('levs') ~= 1)
  levs = 'all';
end

if (exist('bands') ~= 1)
  bands = 'all';
end

if (exist('twidth') ~= 1)
  twidth = 1;
elseif (twidth <= 0)
  fprintf(1,'Warning: TWIDTH must be positive.  Setting to 1.\n');
  twidth = 1;
end

%%------------------------------------------------------------

nbands = spyrNumBands(pind);

maxLev =  1+spyrHt(pind);
if strcmp(levs,'all')
  levs = [0:maxLev]';
else
  if (any(levs > maxLev) | any(levs < 0))
    error(sprintf('Level numbers must be in the range [0, %d].', maxLev));
  end
  levs = levs(:);
end

if strcmp(bands,'all')
  bands = [1:nbands]';
else
  if (any(bands < 1) | any(bands > nbands))
    error(sprintf('Band numbers must be in the range [1,3].', nbands));
  end
  bands = bands(:);
end

%----------------------------------------------------------------------

dims = pind(1,:);
ctr = ceil((dims+0.5)/2);

[xramp,yramp] = meshgrid( ([1:dims(2)]-ctr(2))./(dims(2)/2), ...
    ([1:dims(1)]-ctr(1))./(dims(1)/2) );
angle = atan2(yramp,xramp);
log_rad = sqrt(xramp.^2 + yramp.^2);
log_rad(ctr(1),ctr(2)) =  log_rad(ctr(1),ctr(2)-1);
log_rad  = log2(log_rad);

%% Radial transition function (a raised cosine in log-frequency):
[Xrcos,Yrcos] = rcosFn(twidth,(-twidth/2),[0 1]);
Yrcos = sqrt(Yrcos);
YIrcos = sqrt(abs(1.0 - Yrcos.^2));

if (size(pind,1) == 2)
  if (any(levs==1))
    resdft = fftshift(fft2(pyrBand(pyr,pind,2)));
  else
    resdft = zeros(pind(2,:));
  end
else
  resdft = reconSFpyrLevs(pyr(1+prod(pind(1,:)):size(pyr,1)), ...
      pind(2:size(pind,1),:), ...
      log_rad, Xrcos, Yrcos, angle, nbands, levs, bands);
end

lo0mask = pointOp(log_rad, YIrcos, Xrcos(1), Xrcos(2)-Xrcos(1), 0);
resdft = resdft .* lo0mask;

%% residual highpass subband
if any(levs == 0)
  hi0mask = pointOp(log_rad, Yrcos, Xrcos(1), Xrcos(2)-Xrcos(1), 0);
  hidft = fftshift(fft2(subMtx(pyr, pind(1,:))));
  resdft = resdft + hidft .* hi0mask;
end

res = real(ifft2(ifftshift(resdft)));