1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
#! /usr/bin/env python
print "OpenCV Python version of lkdemo"
import sys
# import the necessary things for OpenCV
import cv2.cv as cv
#############################################################################
# some "constants"
win_size = 10
MAX_COUNT = 500
#############################################################################
# some "global" variables
image = None
pt = None
add_remove_pt = False
flags = 0
night_mode = False
need_to_init = False
#############################################################################
# the mouse callback
# the callback on the trackbar
def on_mouse (event, x, y, flags, param):
# we will use the global pt and add_remove_pt
global pt
global add_remove_pt
if image is None:
# not initialized, so skip
return
if image.origin != 0:
# different origin
y = image.height - y
if event == cv.CV_EVENT_LBUTTONDOWN:
# user has click, so memorize it
pt = (x, y)
add_remove_pt = True
#############################################################################
# so, here is the main part of the program
if __name__ == '__main__':
frames = sys.argv[1:]
if frames == []:
print "usage lkdemo.py <image files>"
sys.exit(1)
# display a small howto use it
print "Hot keys: \n" \
"\tESC - quit the program\n" \
"\tr - auto-initialize tracking\n" \
"\tc - delete all the points\n" \
"\tn - switch the \"night\" mode on/off\n" \
"\tSPACE - next frame\n" \
"To add/remove a feature point click it\n"
# first, create the necessary windows
cv.NamedWindow ('LkDemo', cv.CV_WINDOW_AUTOSIZE)
# register the mouse callback
cv.SetMouseCallback ('LkDemo', on_mouse, None)
fc = 0
while 1:
# do forever
frame = cv.LoadImage(frames[fc])
if image is None:
# create the images we need
image = cv.CreateImage (cv.GetSize (frame), 8, 3)
image.origin = frame.origin
grey = cv.CreateImage (cv.GetSize (frame), 8, 1)
prev_grey = cv.CreateImage (cv.GetSize (frame), 8, 1)
pyramid = cv.CreateImage (cv.GetSize (frame), 8, 1)
prev_pyramid = cv.CreateImage (cv.GetSize (frame), 8, 1)
features = []
# copy the frame, so we can draw on it
cv.Copy (frame, image)
# create a grey version of the image
cv.CvtColor (image, grey, cv.CV_BGR2GRAY)
if night_mode:
# night mode: only display the points
cv.SetZero (image)
if need_to_init:
# we want to search all the good points
# create the wanted images
eig = cv.CreateImage (cv.GetSize (grey), 32, 1)
temp = cv.CreateImage (cv.GetSize (grey), 32, 1)
# the default parameters
quality = 0.01
min_distance = 10
# search the good points
features = cv.GoodFeaturesToTrack (
grey, eig, temp,
MAX_COUNT,
quality, min_distance, None, 3, 0, 0.04)
# refine the corner locations
features = cv.FindCornerSubPix (
grey,
features,
(win_size, win_size), (-1, -1),
(cv.CV_TERMCRIT_ITER | cv.CV_TERMCRIT_EPS, 20, 0.03))
elif features != []:
# we have points, so display them
# calculate the optical flow
features, status, track_error = cv.CalcOpticalFlowPyrLK (
prev_grey, grey, prev_pyramid, pyramid,
features,
(win_size, win_size), 3,
(cv.CV_TERMCRIT_ITER|cv.CV_TERMCRIT_EPS, 20, 0.03),
flags)
# set back the points we keep
features = [ p for (st,p) in zip(status, features) if st]
if add_remove_pt:
# we have a point to add, so see if it is close to
# another one. If yes, don't use it
def ptptdist(p0, p1):
dx = p0[0] - p1[0]
dy = p0[1] - p1[1]
return dx**2 + dy**2
if min([ ptptdist(pt, p) for p in features ]) < 25:
# too close
add_remove_pt = 0
# draw the points as green circles
for the_point in features:
cv.Circle (image, (int(the_point[0]), int(the_point[1])), 3, (0, 255, 0, 0), -1, 8, 0)
if add_remove_pt:
# we want to add a point
# refine this corner location and append it to 'features'
features += cv.FindCornerSubPix (
grey,
[pt],
(win_size, win_size), (-1, -1),
(cv.CV_TERMCRIT_ITER | cv.CV_TERMCRIT_EPS,
20, 0.03))
# we are no longer in "add_remove_pt" mode
add_remove_pt = False
# swapping
prev_grey, grey = grey, prev_grey
prev_pyramid, pyramid = pyramid, prev_pyramid
need_to_init = False
# we can now display the image
cv.ShowImage ('LkDemo', image)
# handle events
c = cv.WaitKey(10) % 0x100
if c == 27:
# user has press the ESC key, so exit
break
# processing depending on the character
if 32 <= c and c < 128:
cc = chr(c).lower()
if cc == 'r':
need_to_init = True
elif cc == 'c':
features = []
elif cc == 'n':
night_mode = not night_mode
elif cc == ' ':
fc = (fc + 1) % len(frames)
cv.DestroyAllWindows()