gray histogram feature的用法和样例：
例句
- The similarity is decided by the Euclidean distance of the gray histograms.
利用各区域灰度直方图的欧氏距离判定相似区域。 - This paper presents a method of determining the type of vehicle-license-plate based on the gradient histogram and the gray histogram of the image of a vehicle-license-plate.
本文提出一种基于车牌图像梯度直方图和灰度直方图确定车牌类型的方法。
