--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/python/compute-homography.py	Tue Sep 06 17:55:06 2011 -0400
@@ -0,0 +1,40 @@
+#! /usr/bin/env python
+
+import sys,getopt
+
+import numpy as np
+import cv2
+
+import cvutils
+import utils
+
+options, args = getopt.getopt(sys.argv[1:], 'h',['help','video_frame='])
+options = dict(options)
+
+if '--help' in options.keys() or '-h' in options.keys():
+    print('''The argument should be the name of a file containing at least 4 non-colinear point coordinates:
+ - the first two lines are the x and y coordinates in the projected space (usually world space)
+ - the last two lines are the x and y coordinates in the origin space (usually image space)''')
+    sys.exit()
+
+if len(args) == 0:
+    print('Usage: {0} --help|-h [--video_frame <video frame filename>] [<point_correspondences.txt>]'.format(sys.argv[0]))
+    sys.exit()
+
+points = np.loadtxt(args[0], dtype=np.float32)
+srcPts = points[2:,:].T
+dstPts = points[:2,:].T
+homography, mask = cv2.findHomography(srcPts, dstPts) # method=0, ransacReprojThreshold=3
+np.savetxt(utils.removeExtension(sys.argv[1])+'-homography.txt',homography)
+
+if '--video_frame' in options.keys() and homography.size>0:
+    img = cv2.imread(options['--video_frame'])
+    for p in srcPts:
+        cv2.circle(img,tuple(p),2,cvutils.cvRed)
+    invHomography = np.linalg.inv(homography)
+    projectedDstPts = cvutils.projectArray(invHomography, dstPts.T).T
+    for i,p in enumerate(projectedDstPts):
+        cv2.circle(img,tuple(np.int32(np.round(p))),2,cvutils.cvBlue)
+        print('img: {0} / projected: {1}'.format(srcPts[i], p))
+    cv2.imshow('video frame',img)
+    cv2.waitKey()