public span_image_filter_gray_bilinear(source_type src, 
                                 interpolator_type inter) :
     base(src, inter, 0) 
 {}
 public span_image_resample_gray(source_type src, 
                          interpolator_type inter,
                          image_filter_lut filter) :
     base(src, inter, filter)
 {}
 public span_image_filter_gray_2x2(source_type src, 
                            interpolator_type inter,
                            image_filter_lut filter) :
     base(src, inter, &filter) 
 {}
 public span_image_filter_gray_bilinear_clip(source_type src, 
                                      color_type back_color,
                                      interpolator_type inter) :
     base(src, inter, 0)
 {
     m_back_color = (back_color);
 }
 public span_image_filter_gray(source_type src,
                               interpolator_type inter,
                               image_filter_lut filter) :
     base(src, inter, filter)
 {
 }
 public span_image_filter_gray_bilinear(source_type src,
                                        interpolator_type inter) :
     base(src, inter, 0)
 {
 }