依公式 黄 =（红 + 绿）/ 2 ，灰度 = （黄 + 蓝）/ 2 ，将红、绿、蓝三种颜色构成的色彩空间映射到由黄、蓝两种颜色构成的色彩空间，进一步取值黑、蓝、灰、黄和白五种，这包括了车牌识别所需要的车牌色（蓝、黄、白、黑）和字符色（白、黑），且灰能保留图像的识别信息，克服二值化阈值缺陷；基于三值图像的车牌识别包括基于三值图像的字符识别和基于三值图像的按分割反推的车牌定位，是建立在三值图像基础上的创新的车牌识别算法体系。-According to the formula Yellow = (red+ green)/2, gray = (yellow+ blue)/2, the red, green, blue three colors of the color space is mapped to the yellow and blue colors constitute the color space, further value black, blue, gray, yellow and white five, which includes the required license plate license plate identification color (blue, yellow, white, black) and character color (white, black), and to preserve the image gray identifying information, to overcome the binarization threshold defects　three-valued image based on license plate recognition, including three-valued image based on character recognition and image-based three-valued inverse of the separator plate positioning, the image is built on the basis of three-valued on the license plate recognition algorithm innovation system.