I was playing with some image recognition techniques in python / OpenCV the other day and couldn't really find an easy way to store and retrieve SURF, SIFT, or ORB keypoint feature sets and their corresponding descriptors.
I quickly wrote these two functions which use pickle to store and retrieve keypoints and descriptors:
def pickle_keypoints(keypoints, descriptors): i = 0 temp_array =  for point in keypoints: temp = (point.pt, point.size, point.angle, point.response, point.octave, point.class_id, descriptors[i]) ++i temp_array.append(temp) return temp_array def unpickle_keypoints(array): keypoints =  descriptors =  for point in array: temp_feature = cv2.KeyPoint(x=point,y=point,_size=point, _angle=point, _response=point, _octave=point, _class_id=point) temp_descriptor = point keypoints.append(temp_feature) descriptors.append(temp_descriptor) return keypoints, np.array(descriptors)
Usage would be something like this:
import cv2 import numpy as np import cPickle as pickle # Load the images img1 =cv2.imread('test_img1.jpg') img2 =cv2.imread('test_img2.jpg') # Convert them to greyscale grey_img1 =cv2.cvtColor(img1,cv2.COLOR_BGR2GRAY) grey_img2 =cv2.cvtColor(img2,cv2.COLOR_BGR2GRAY) # SURF extraction surf = cv2.SURF() kp1, desc1 = surf.detect(grey_img1,None,useProvidedKeypoints = False) kp2, desc2 = surf.detect(grey_img2,None,useProvidedKeypoints = False) #Store and Retrieve keypoint features temp_array =  temp = pickle_keypoints(kp1, desc1) temp_array.append(temp) temp = pickle_keypoints(kp2, desc2) temp_array.append(temp) pickle.dump(temp_array, open("keypoints_database.p", "wb")) #Retrieve Keypoint Features keypoints_database = pickle.load( open( "keypoints_database.p", "rb" ) ) kp1, desc1 = unpickle_keypoints(keypoints_database) kp1, desc1 = unpickle_keypoints(keypoints_database)
Laird P Foret firstname.lastname@example.org
Laird Foret has over 28 years of experience in the IT industry and is responsible for the day-to-day operations and administration of isotope|eleven, inc. Prior to founding isotope|eleven in 2005, he started and ran many various companies and considers himself a serial entrepreneur. He graduated from Millsaps College in Computer Science and has a minor in accounting.