利用sift算法pythonopen检测多个目标

Question

如何使用sift算法检测多个对象。我可以单独检测单个对象，但无法找出在一个代码中检测多个对象的方法。在

import cv2

import numpy as np

MIN_MATCH_COUNT=30

detector=cv2.SIFT()

FLANN_INDEX_KDITREE=0

flannParam=dict(algorithm=FLANN_INDEX_KDITREE,tree=5)

flann=cv2.FlannBasedMatcher(flannParam,{})

trainImg=cv2.imread("training/one.jpeg",0)

trainKP,trainDesc=detector.detectAndCompute(trainImg,None)

cam=cv2.VideoCapture(0)

while True:
    ret, QueryImgBGR=cam.read()

    QueryImg=cv2.cvtColor(QueryImgBGR,cv2.COLOR_BGR2GRAY)
    queryKP,queryDesc=detector.detectAndCompute(QueryImg,None)
    matches=flann.knnMatch(queryDesc,trainDesc,k=2)

    goodMatch=[]
    for m,n in matches:
        if(m.distance<0.75*n.distance):
            goodMatch.append(m)
    if(len(goodMatch)>MIN_MATCH_COUNT):
        tp=[]
        qp=[]
        for m in goodMatch:
            tp.append(trainKP[m.trainIdx].pt)
            qp.append(queryKP[m.queryIdx].pt)
        tp,qp=np.float32((tp,qp))
        H,status=cv2.findHomography(tp,qp,cv2.RANSAC,3.0)
        h,w=trainImg.shape
        trainBorder=np.float32([[[0,0],[0,h-1],[w-1,h-1],[w-1,0]]])
        queryBorder=cv2.perspectiveTransform(trainBorder,H)
        cv2.polylines(QueryImgBGR,[np.int32(queryBorder)],True,(0,255,0),5)

        cv2.putText(QueryImgBGR,'Stop sign detected!', 
        (0,300), 
        cv2.FONT_HERSHEY_SIMPLEX, 
        1,
        (255,0,0),
        2)

        cv2.putText(QueryImgBGR,'Apply brakes instantly', 
        (0,350), 
        cv2.FONT_HERSHEY_SIMPLEX, 
        1,
        (255,0,0),
        2)

    else:
        print "Not Enough match found- %d/%d"%(len(goodMatch),MIN_MATCH_COUNT)
    cv2.imshow('result',QueryImgBGR)
    if cv2.waitKey(10)==ord('q'):
        break
cam.release()
cv2.destroyAllWindows()