Reconstruct the input image using the method of filtered back projection

  function PushButton2Selected(h, eventdata)
    switch list1_val
      case 'None'
        filter_val = 'None';
      case 'Ram-Lak (Ramp)'
        filter_val = 'Ram-Lak';
      case 'Shepp-Logan'
        filter_val = 'Shepp-Logan';
      case 'Ram-Lak Cosine'
        filter_val = 'Cosine';
      case 'Ram-Lak Hamming'
        filter_val = 'Hamming';
      case 'Ram-Lak Hann'
        filter_val = 'Hann';
      case 'Special'
        filter_val = 'Special';
    end
    
    switch list2_val
      case 'Linear'
        interpol_val = 'linear';
      case 'Nearest'
        interpol_val = 'nearest';
      case 'Spline'
        interpol_val = 'spline';
      case 'Cubic'
        interpol_val = 'pchip';
    end

    theta = round (0: 180 / number_projections: 179);
    del_sinogram = data.sinogram (:, theta + 1);

    if strcmp(filter_val, 'Special') == 1
      if strcmp(file_name(end-4:end), '3.mat') == 1
        data.SB = data.SB + 0.3 * rand(size(data.SB));
      end
      
      if strcmp(file_name(end-4:end), 'f.mat') == 1
        filter_val = 'Hamming';
        rec_img = iradon(del_sinogram, theta, interpol_val, filter_val);
      else
        FFT_sinogram = fftshift(fft(del_sinogram),1);
        FFT_sinogram = FFT_sinogram .* data.SB(:, theta+1);
        del_sinogram = ifft(ifftshift(FFT_sinogram,1));
        rec_img = iradon(del_sinogram, theta, interpol_val);
      end
    else
      rec_img = iradon(del_sinogram, theta, interpol_val, filter_val);
    end
    
    figure, imagesc (rec_img), colormap (pink)
    title ([data.txt ':' num2str (number_projections) 'projections,' list1_val 'filter,' list2_val 'interpolation'])
  end

D-023