用3中误差扩散滤波器实现误差扩散，分别是floyd stein, sierra, Stenenson滤波器-Error diffusion filter with a 3 to achieve error diffusion, respectively, floyd stein, sierra, Stenenson filter

本程序实现了两种误差扩散算法，分别用Sierra扩散滤波器和stenenson扩散滤波器，实现了比Floy_stein更好的误差扩散半色调效果。-This procedure implements two error diffusion algorithm, respectively Sierra diffusion filters and stenenson diffusion filter, to achieve better than Floy_stein error diffusion