用matlab实现改变图像灰度值，输出依次为原图像（灰度值256），128,64,32,16,8,4,2-Reducing the Number of Gray Levels in an Image (a) Write a computer program capable of reducing the number of gray levels in an image 256 to 2, in integer（整数） powers of 2. The desired number

降低图像灰度级 在不能使用imadjust函数的情况下，采用利用矩阵进行像素运算的方法。(1. Reducing the Number of Gray Levels in an Image (a) Write a computer program capable of reducing the number of gray levels in an image from 256 to 2, in integer powers of 2. The desired number of gr