opencv学习——cv2.drawMatches()与cv2.drawMatchesKnn()区别

1、提取两幅图像特征之后，画出匹配点对连线。

good = []
for m,n in matches:
     if m.distance < 0.75*n.distance:
        good.append(m)

2、区别：
cv2.drawMatches()使用的点对集good是一维的，（N，）；
matchesMask是计算转换H矩阵时生成的掩模，inliers的点，最后只画出符合条件的inliers点对。

    draw_params = dict(matchColor = (0,255,0), # draw matches in green color
    singlePointColor = None,
    matchesMask = matchesMask, # draw only inliers
    flags = 2)
    img3 = cv2.drawMatches(img1,kp1,img2,kp2,good,None,**draw_params)

或者直接使用

img3 = cv2.drawMatches(img1,kp1,img2,kp2,good,None,matchesMask = matchesMask,flags=2)

cv2.drawMatchesKnn()使用的点对集good是一维的，（N，1）；画出good中前几个点对连线；

good = np.expand_dims(good,1)
img3 = cv2.drawMatchesKnn(img1,kp1,img2,kp2,good[:20],None, flags=2)