使用抖动创建图像。使用抖动得到的图像看上去有更多的颜色数；不适用抖动得到的图像看上去颜色数少，大门空间分辨率要高些。-Creating images using dithering. Jitter by using the image appears to have more number of colors　not apply to jitter resulting image looks small number of colors, the door to higher spatial resolution.