The linear darkness transform method is used to increase the contrastiveness of pictures ; the improved mid - value filtering algorithm and local average method are adopted to protect the edge as much as possible on the basis of noise elimination 采用线性灰度变换等方法对图像进行增强，使图像的对比度扩展。采用改进型中值滤波法和多图像平均法，在去除了噪声的基础上尽可能的保护了边缘。
