RET is the set of all items the system has retrieved for a specific inquiry

matlab中一些对图片进行处理的小程序，包括ostu阈值分割，rgb2lab空间的转换，sobel边缘检测，自适应阈值分割-Some small programs，including ostu、rgb2lab、sobel、Adaptive thresholding（matlab）

opencv编程，将RGB转换成lab空间显示，可以运行，代码比较短，容易理解。-opencv programming, lab space will be converted to RGB display, you can run, the code is relatively short and easy to understand.