说明：  图像检索——提取颜色特征：HSV空间颜色直方图(将RGB空间转化为HSV空间并进行非等间隔量化，将三个颜色分量表示成一维矢量，再计算其直方图作为颜色特征。
(Image Retrieval- extract color features: HSV space color histogram (RGB space into the HSV space and the non-interval to quantify the three color components expressed as a one-dimensional vector, then calculate the color histogram as a feature.)