function h=psfgenerate(type,n,options)

if type == 1
% Guassian
      h = fftshift(normal_pdf(linspace(-2,2,n),0,0.0015))';
      h = real(ifft(fft(h)));
      d = getoptions(options, 'dim', 1); 
      if d==2,	h = h*h';
      end
elseif type == 2
% Moving-Average 
      q = getoptions(options, 'param', 9);
      h = shift([ ones(1,q) , zeros(1, n-q)]'/q,-floor(q/2));
      d = getoptions(options, 'dim', 1); 
      if d==2,	h = h*h';
      end
elseif type == 3
% Exponential
      nu = getoptions(options, 'param', 0.5);
      h = fftshift(exp(-abs([-n/2:n/2-1]').^nu));
      d = getoptions(options, 'dim', 1); 
      if d==2,	h = h*h';
      end
elseif type == 4
% Algebraic
      nu = getoptions(options, 'param', 1);
      d = getoptions(options, 'dim', 1); 
      if d==2,	
      	[Ii,Ji] = meshgrid([-n/2:n/2-1],[-n/2:n/2-1]);
      	h = fftshift(1./(1 + abs(Ii) + abs(Ji)).^nu);
      else
        h = fftshift(1./(1 + abs([-n/2:n/2-1])).^nu);
      end
elseif type == 5
% Spherically-symmetric 1/f
      %q  = 7;
      %[Ii,Ji] = meshgrid([-q:q-1],[-q:q-1]);
      [Ii,Ji] = meshgrid([-n/2:n/2-1],[-n/2:n/2-1]);
      h = fftshift(1./(1 + Ii.^2 + Ji.^2));
      %h = zeros(n,n);
      %h(end/2-q+1:end/2+q,end/2-q+1:end/2+q) = 1./(1 + Ii.^2 + Ji.^2);
      %h = fftshift(h);
elseif type == 6
% The r used below is the same as that used in the Kalifa paper.
      r = getoptions(options, 'param', 1);
      fft_row = [ones(1,n/4) (2^r) * (abs( 2*((n/4+1):(n/2))/(n)-1)).^r ] ; 
      sum1 = norm([ fft_row  fliplr(fft_row)]);
      fft_row = [ fft_row  fliplr(fft_row)];
      fft_row(~fft_row) = 1E-5;
      sum2 = norm(fft_row(:));
      fft_row = fft_row*sum1/sum2;  
      h_row   = real(ifft(fft_row));
      h_row = h_row(:);
      clear fft_col
      h_col = h_row;
      h = h_col * h_row.';
elseif type == 7
% Dirac
      h = zeros(n,n);h(1,1)=1;
else
      error('You did not specify any valid PSF')
end