带有 opencv 2.4.6.1 和 Python 的 SURF 描述符

Question

我正在使用 Python 和 opencv 进行 SURF 特征检测。我在 stackoverflow OpenCV 2.4.1 - computing SURF descriptors in Python 上找到了这些示例，但不幸的是，它们不适用于最新版本的 opencv，即 2.4.6.1。 cv2.SURF.detect() 命令必须已更改，因为它现在只允许两个参数：

cv2.SURF.detect(image[, mask]) → keypoints¶

所以我只能得到关键点，但是我如何得到描述符呢？没有找到解决方案。希望你能在这里帮助我。谢谢

Answer 1

根据 Abid Rahman K 在 cmets 中发布的教程，我修改了此示例代码 OpenCV 2.4.1 - computing SURF descriptors in Python，使其适用于 opencv 2.4.6.1

获取SURF关键点和描述符的函数已更改为：

cv2.SURF.detectAndCompute(image, mask[, descriptors[, useProvidedKeypoints]]) → keypoints, descriptors

所以这里是链接的修改示例：

import cv2
import numpy

opencv_haystack =cv2.imread('haystack.jpg')
opencv_needle =cv2.imread('needle.jpg')

ngrey = cv2.cvtColor(opencv_needle, cv2.COLOR_BGR2GRAY)
hgrey = cv2.cvtColor(opencv_haystack, cv2.COLOR_BGR2GRAY)

# build feature detector and descriptor extractor
hessian_threshold = 5000
detector = cv2.SURF(hessian_threshold)
hkeypoints,hdescriptors = detector.detectAndCompute(hgrey,None)
nkeypoints,ndescriptors = detector.detectAndCompute(ngrey,None)

# extract vectors of size 64 from raw descriptors numpy arrays
rowsize = len(hdescriptors) / len(hkeypoints)
if rowsize > 1:
    hrows = numpy.array(hdescriptors, dtype = numpy.float32).reshape((-1, rowsize))
    nrows = numpy.array(ndescriptors, dtype = numpy.float32).reshape((-1, rowsize))
    #print hrows.shape, nrows.shape
else:
    hrows = numpy.array(hdescriptors, dtype = numpy.float32)
    nrows = numpy.array(ndescriptors, dtype = numpy.float32)
    rowsize = len(hrows[0])

# kNN training - learn mapping from hrow to hkeypoints index
samples = hrows
responses = numpy.arange(len(hkeypoints), dtype = numpy.float32)
#print len(samples), len(responses)
knn = cv2.KNearest()
knn.train(samples,responses)

# retrieve index and value through enumeration
for i, descriptor in enumerate(nrows):
    descriptor = numpy.array(descriptor, dtype = numpy.float32).reshape((1, rowsize))
    #print i, descriptor.shape, samples[0].shape
    retval, results, neigh_resp, dists = knn.find_nearest(descriptor, 1)
    res, dist =  int(results[0][0]), dists[0][0]
    #print res, dist

    if dist < 0.1:
        # draw matched keypoints in red color
        color = (0, 0, 255)
    else:
        # draw unmatched in blue color
        color = (255, 0, 0)
    # draw matched key points on haystack image
    x,y = hkeypoints[res].pt
    center = (int(x),int(y))
    cv2.circle(opencv_haystack,center,2,color,-1)
    # draw matched key points on needle image
    x,y = nkeypoints[i].pt
    center = (int(x),int(y))
    cv2.circle(opencv_needle,center,2,color,-1)

cv2.imshow('haystack',opencv_haystack)
cv2.imshow('needle',opencv_needle)
cv2.waitKey(0)
cv2.destroyAllWindows()