该程序首先把rgb图像转化为XYZ空间，然后在XYZ空间进行一些阈值找到黄色的底色车牌，这是从国外的车牌识别程序，但不明白那些阈值为什么要那么设，用的是什么原理？

还有一个疑问就是，这个程序对于输入的车牌有时候找到的是车牌的底，有时候是车牌的数字。一个是黄色，一个是白色。真不知道怎么找的。-The program first rgb image into XYZ space, and then in the XYZ space to some threshold to find a yellow background plates, this is from a foreign license plate recognition program, but those who do not understand why the threshold then set up, using the What is the principle? There is also a doubt is that this procedure for the importation of the license plate is sometimes found at the end of license plates, and sometimes the number of plates. One is yellow, one is white. Really do not know how to find.