function reconstruction
clear;
close all;
N=256;%N＊N size image
delta=3; %equivalent to Φ
a = 100;
b = 50;
d = 1;
%Generate ellipse
for m =1:180/delta;
L =a^2*cos(m*delta)^2+b^2*sin(m*delta)^2;
for t=-N/2+1:N/2;
if (t^2 <= L)
proj(t+N/2,m)=2*a*b*sqrt(Lt^2)/L;
else
proj(t+N/2,m)=0;
end
end
end
%%%% various filtering Function
for t = -N+1:N-1;
h1(t+N)=-2/(pi^2*d^2*(4*t^2-1));% SL
end;
for t= -N+1:N-1;
if t==0
h2(t+N)=1/(4*d^2);% RL
elseif mod(t,2) == 1
h2(t+N)=-1/(t^2*pi^2*d^2);
else
h2(t+N)=0;
end;
end;
% Lewitt
esp=0.5;
for t=-N+1:N-1;
if t==0
h3(t+N)=(1-2*esp/3)/(4*d^2);
elseif mod(t,2)==1
h3(t+N)=-(1-esp)/(t^2*pi^2*d^2);
else
h3(t+N)=-esp/(t^2*pi^2*d^2);
end;
end;
%存储各种反投影结果
rProj1=zeros(N,N);
rProj2=zeros(N,N);
rProj3=zeros(N,N);
rProj4=zeros(N,N);
nProj=[];
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