如何在opencv flann上实现余弦度量(knnsearch)

Question

我正在使用opencv flann索引在数据库中搜索图像。正如我在文档中看到的，flann提供了如下指标：

   FLANN_DIST_EUCLIDEAN = 1,
    FLANN_DIST_L2 = 1,
    FLANN_DIST_MANHATTAN = 2,
    FLANN_DIST_L1 = 2,
    FLANN_DIST_MINKOWSKI = 3,
    FLANN_DIST_MAX   = 4,
    FLANN_DIST_HIST_INTERSECT   = 5,
    FLANN_DIST_HELLINGER = 6,
    FLANN_DIST_CHI_SQUARE = 7,
    FLANN_DIST_CS         = 7,
    FLANN_DIST_KULLBACK_LEIBLER  = 8,
    FLANN_DIST_KL                = 8,
    FLANN_DIST_HAMMING          = 9,

没有余弦距离那么，如何将其实现到opencv库中呢？谢谢

Answer 1

这是几年前在flann github资源库中提出的。(请参阅this issue。)要点(据我所理解)是余弦相似度不是距离度量。在这个问题上有更深层次的解释。