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#! /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()
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