对512x512的lenagray.jpg图像分别采样为256x256、128x128、64x64的图像； 对lenagray.jpg图像分别量化为64级灰度图像、32级灰度图像、8级灰度图像和4级灰度图像。(The lenagray. jpg images of 512x512 were sampled as 256x256, 128x128 and 64x64 images respectively. The lenagray.jpg image is quantized into 64-l