ctw.m

3D--ART重建

%--投影矩阵W--good
%--w投影矩阵，M,N网格划分，I射线条数，J象素个数，K投影方向数，S每方向投影数
function [W,N,I,J]=ctw(K,N,S)
%K=4;S=26;N=26;
M=N;lx=1/(M-1);ly=1/(N-1);d=1/(S-1);a=pi/K;I=K*S;J=M*N;
W=[];
	for k=0:K-1
		for s=0:S-1
            t=-1/2*(1-sqrt(2)*sin(-k*a+pi/4))+s*d;
			for n=0:(N-1)
				for m=0:(M-1)
					i=k*S+s+1;
					j=n*M+m+1;
					if abs(tan(k*a))>=0&abs(tan(k*a))<=1
					W(i,j)=lx*abs(sec(k*a))*sinc((t*sec(k*a)+m*lx*tan(k*a)-n*ly)/ly);
					elseif abs(tan(k*a))>1&abs(tan(k*a))<inf
						W(i,j)=ly*abs(sec(k*a))/abs(tan(k*a))*sinc((t*sec(k*a)+m*lx*tan(k*a)-n*ly)/(lx*tan(k*a)));
                    elseif abs(tan(k*a))==inf
						W(i,j)=ly*sinc((t+m*lx)/lx);
                    end
                end
            end
        end
    end