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comparison python/compute-homography.py @ 151:4af774bb186d

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wrote a simple script to compute homography from point correspondences and display the reprojection for visual verification
author Nicolas Saunier <nicolas.saunier@polymtl.ca>
date Tue, 06 Sep 2011 17:55:06 -0400
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children b0719b3ad3db
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150:404f3cade05f 151:4af774bb186d
1 #! /usr/bin/env python
2
3 import sys,getopt
4
5 import numpy as np
6 import cv2
7
8 import cvutils
9 import utils
10
11 options, args = getopt.getopt(sys.argv[1:], 'h',['help','video_frame='])
12 options = dict(options)
13
14 if '--help' in options.keys() or '-h' in options.keys():
15 print('''The argument should be the name of a file containing at least 4 non-colinear point coordinates:
16 - the first two lines are the x and y coordinates in the projected space (usually world space)
17 - the last two lines are the x and y coordinates in the origin space (usually image space)''')
18 sys.exit()
19
20 if len(args) == 0:
21 print('Usage: {0} --help|-h [--video_frame <video frame filename>] [<point_correspondences.txt>]'.format(sys.argv[0]))
22 sys.exit()
23
24 points = np.loadtxt(args[0], dtype=np.float32)
25 srcPts = points[2:,:].T
26 dstPts = points[:2,:].T
27 homography, mask = cv2.findHomography(srcPts, dstPts) # method=0, ransacReprojThreshold=3
28 np.savetxt(utils.removeExtension(sys.argv[1])+'-homography.txt',homography)
29
30 if '--video_frame' in options.keys() and homography.size>0:
31 img = cv2.imread(options['--video_frame'])
32 for p in srcPts:
33 cv2.circle(img,tuple(p),2,cvutils.cvRed)
34 invHomography = np.linalg.inv(homography)
35 projectedDstPts = cvutils.projectArray(invHomography, dstPts.T).T
36 for i,p in enumerate(projectedDstPts):
37 cv2.circle(img,tuple(np.int32(np.round(p))),2,cvutils.cvBlue)
38 print('img: {0} / projected: {1}'.format(srcPts[i], p))
39 cv2.imshow('video frame',img)
40 cv2.waitKey()