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Python opencv ORB compatible

hi im works in Matching Features with python opencv ORB, but when I run this code I get this Traceback error (last last call): File "ffl.py", line 27, in for m, n in matches: TypeError: object 'cv2.DMatch' is not iterable

I do not know how to fix this.

import numpy as np import cv2 import time ESC=27 camera = cv2.VideoCapture(0) orb = cv2.ORB_create() bf = cv2.BFMatcher(cv2.NORM_HAMMING, crossCheck=True) imgTrainColor = cv2.imread('/home/shar/home.jpg') imgTrainGray = cv2.cvtColor(imgTrainColor, cv2.COLOR_BGR2GRAY) kpTrain = orb.detect(imgTrainGray,None) kpTrain, desTrain = orb.compute(imgTrainGray, kpTrain) firsttime = True while True: ret, imgCamColor = camera.read() imgCamGray = cv2.cvtColor(imgCamColor, cv2.COLOR_BGR2GRAY) kpCam = orb.detect(imgCamGray,None) kpCam, desCam = orb.compute(imgCamGray, kpCam) bf = cv2.BFMatcher(cv2.NORM_HAMMING, crossCheck=True) matches = bf.match(desCam,desTrain) good = [] for m,n in matches: if m.distance < 0.7*n.distance: good.append(m) if firsttime==True: h1, w1 = imgCamColor.shape[:2] h2, w2 = imgTrainColor.shape[:2] nWidth = w1+w2 nHeight = max(h1, h2) hdif = (h1-h2)/2 firsttime=False result = np.zeros((nHeight, nWidth, 3), np.uint8) result[hdif:hdif+h2, :w2] = imgTrainColor result[:h1, w2:w1+w2] = imgCamColor for i in range(len(matches)): pt_a=(int(kpTrain[matches[i].trainIdx].pt[0]), int(kpTrain[matches[i].trainIdx].pt[1]+hdif)) pt_b=(int(kpCam[matches[i].queryIdx].pt[0]+w2), int(kpCam[matches[i].queryIdx].pt[1])) cv2.line(result, pt_a, pt_b, (255, 0, 0)) cv2.imshow('Camara', result) key = cv2.waitKey(20) if key == ESC: break cv2.destroyAllWindows() camera.release()
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1 answer

bf.match returns only a list of individual objects, you cannot bf.match over it using m, n. Maybe you are confused with bf.knnMatch ?

You can simply change your code to:

 for m in matches: if m.distance < 0.7: good.append(m)

From the Python OpenCV tutorials ( link ):

The result of match = bf.match (des1, des2) line is a list of DMatch objects. This DMatch object has the following attributes:

  • DMatch.distance - The distance between the descriptors. The lower the better.
  • DMatch.trainIdx - descriptor index in train descriptors
  • DMatch.queryIdx - descriptor index in query descriptors
  • DMatch.imgIdx - index image of the train.
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