灰度图像的量化和直方图均衡化直接调用函数。量化是指将像素灰度转换成离散的整数值的过程。量化等级越多，所得图像层次越丰富，灰度分辨率高，图像质量好，但数据量大。-Write MATLAB functions to quantize grayscale image with given quantization step Q. Process the given test images “Lena” with quantization steps Q=2, 4, 8 16, 32, 64, 1