中文说明：资源描述 影像的数字说明了地物的反射率大小。但是如果获取数值差异不大，显示为影像地物色彩不容易区分（整体偏暗、偏亮），即对比度小，则会影响有用信息的提取。 因此需要一种数学方法，来合理的扩大信息差异。即改变像元数值大小。方法有多种： 使大数值更大，小数值更小，扩大差异 使过小的数值变大，过大的数值变小，缩小没有必要的距离。 这些方法对应了不同的对比度拉伸功能。
English Description：
Application backgroundThe digital image shows the reflectivity of the object. But if the difference is not big, it is not easy to distinguish the color of the image features (the whole is dark, bright), that is, the contrast is small, it will affect the extraction of useful information.Therefore, a mathematical method is needed to expand the information difference. That is to change the value of the pixel value. There are many ways to:To make larger, smaller, smaller, and expand the differenceTo make too small, too large, too large to become small, to narrow the distance without the need.These methods correspond to different contrast stretching functions.