opencv--ORB::create

static Ptr<ORB> cv::ORB::create (

                        int nfeatures = 500,

                         float scaleFactor = 1.2f,

                        int nlevels = 8,

                        int edgeThreshold = 31,

                        int firstLevel = 0,

                         int WTA_K = 2,

                         int scoreType = ORB::HARRIS_SCORE,

                         int patchSize = 31,

                         int fastThreshold = 20

                     ) 

nfeatures:表示取的特征點數量

float scaleFactor = 1.2f   ：表示每一層與上一層的比例關系

int nlevels = 8,：圖像金字塔的層數

edgeThreshold = 31,預設吧，看不懂解釋

firstLevel = 0,  預設吧，看不懂解釋

int WTA_K = 2, 表示描述符随機數的範圍，2表示描述符的數字随機取0，1。3表示随機取0，1，2。一般都是2

scoreType = ORB::HARRIS_SCORE,這表示用harris特征來給定分數。一般預設用這個。

patchSize = 31,預設吧，看不懂解釋

fastThreshold = 20預設吧，看不懂解釋

英文詳解：

https://docs.opencv.org/3.2.0/db/d95/classcv_1_1ORB.html#adc371099dc902a9674bd98936e79739c