将LENA图像分别进行4倍和16倍减采样并对减采样的效果进行描述 将LENA图像转换成256、62、32、8、2 级灰度图像，并对灰度减小后的图像效果进行-Will LENA image separately and 16 times as much as four times and reduce sampling the effects of reducing sampling the LENA images into 256, 62, 32, 8, 2 levels of gray ima