图像增强：空域增强；灰度直方图；平滑滤波器和锐化滤波器的使用；图像中值滤波增强的使用；低通滤波器和高通滤波器的使用

-Image Enhancement: Enhanced airspace　gray histogram　use of the smoothing filter and sharpening filter　the use of the enhanced image median filtering　the use of low-pass filter and high-pass filter