bow训练器添加图片特征时出现错误：cv2.error:和error: (-215)

要天天睡好觉 2017-10-12 12:46:46

最近自己想学着创建一个物体检测器，但跑得时候出现错误。代码参考了《OpenCV3计算机视觉Python语言实现第二版》的第七章代码，python版本为3.5.4，opencv版本为3.3.0。代码如下：

import cv2

import numpy as np

from os.path import join



# placeholder path

datapath = "trainimages/"

def path(cls,i):

  return "%s/%s%d.pgm"  % (datapath,cls,i+1)



pos, neg = "pos", "neg"



detect = cv2.xfeatures2d.SIFT_create()

extract = cv2.xfeatures2d.SIFT_create()



flann_params = dict(algorithm = 1, trees = 5)

matcher = cv2.FlannBasedMatcher(flann_params, {})



bow_kmeans_trainer = cv2.BOWKMeansTrainer(40)

extract_bow = cv2.BOWImgDescriptorExtractor(extract, matcher)



def extract_sift(fn):

  im = cv2.imread(fn,0)

  return extract.compute(im, detect.detect(im))[1]

  

for i in range(8):

  bow_kmeans_trainer.add(extract_sift(path(pos,i)))

  bow_kmeans_trainer.add(extract_sift(path(neg,i)))

  

voc = bow_kmeans_trainer.cluster()

extract_bow.setVocabulary( voc )



def bow_features(fn):

  im = cv2.imread(fn,0)

  return extract_bow.compute(im, detect.detect(im))



traindata, trainlabels = [],[]

for i in range(20): 

  traindata.extend(bow_features(path(pos, i))); trainlabels.append(1)

  traindata.extend(bow_features(path(neg, i))); trainlabels.append(-1)



svm = cv2.ml.SVM_create()

svm.train(np.array(traindata), cv2.ml.ROW_SAMPLE, np.array(trainlabels))



def predict(fn):

  f = bow_features(fn);  

  p = svm.predict(f)

  print (fn, "\t", p[1][0][0])

  return p



# again placeholder paths

car, notcar = "xxmd3,jpg", "no.jpg"

car_img = cv2.imread(car)

notcar_img = cv2.imread(notcar)

car_predict = predict(car)

not_car_predict = predict(notcar)



font = cv2.FONT_HERSHEY_SIMPLEX



if (car_predict[1][0][0] == 1.0):

  cv2.putText(car_img,'Detected',(10,30), font, 1,(0,255,0),2,cv2.LINE_AA)



if (not_car_predict[1][0][0] == -1.0):

  cv2.putText(notcar_img,' Not Detected',(10,30), font, 1,(0,0, 255),2,cv2.LINE_AA)



cv2.imshow('BOW + SVM Success', car_img)

cv2.imshow('BOW + SVM Failure', notcar_img)

cv2.waitKey(0)

cv2.destroyAllWindows()

运行的时候出现错误：
Traceback (most recent call last):
File "G:\python test demo\test1012\text.py", line 26, in <module>
bow_kmeans_trainer.add(extract_sift(path(pos,i)))
cv2.error: D:\Build\OpenCV\opencv-3.3.0\modules\features2d\src\bagofwords.cpp:55: error: (-215) !_descriptors.empty() in function cv::BOWTrainer::add
我在d盘找不到bagofwords.cpp文件，路径不存在。后面的错误也看不明白，恳请大神帮忙看看，具体错误错在什么地方，万分感谢！！

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