invradon_zp2_fast.m

beamlet变化的工具箱

function x = InvRadon_Zp2_Fast(Rad)
% InvRadon_Zp2_Fast: Fast Inverse Radon Transform for Z_p^2
% Usage
%	x = Inv_Radon_Zp2(Rad)
% Inputs
%	Rad	array p*(p+1)
% Outputs 
%	x	array p*p, p prime
% Description
%	An O(p^2 log(p)) flops algorithm for the
%	Inverse Radon transform for Z_p^2.
%
p = size(Rad,1);
Ave = mean(Rad(:,1));
Rad = Rad - Ave;
PPolar = zeros(p,p+1);
for i=1:(p+1),
  PPolar(:,i) = fft(Rad(:,i)) ./ p;
end
fhat = zeros(p,p);
fhat(1,1:p) = PPolar(:,(p+1)).';
for i=0:(p-1),
	row = 0:(p-1);
	col = rem( -i.* row, p);
	col = col + (col ~= 0) .*  p;
	inx = row + p*col + 1;
	vec = PPolar(:,i+1); 
    fhat(inx) = vec(:);
end
x = ifft2(fhat) .* p^2;
x = real(x);
x = x + Ave;

% Copyright 2000  David L. Donoho

%
% Part of BeamLab Version:200
% Built:Friday,23-Aug-2002 00:00:00
% This is Copyrighted Material
% For Copying permissions see COPYING.m
% Comments? e-mail [e-mail]
%
%
% Part of BeamLab Version:200
% Built:Saturday,14-Sep-2002 00:00:00
% This is Copyrighted Material
% For Copying permissions see COPYING.m
% Comments? e-mail [e-mail]
%