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Lucas Kanade Tracker (OpenCV)
import cv2
import numpy as np
import itertools
lk_params = dict( winSize = (10, 10),
maxLevel = 5,
criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03))
feature_params = dict( maxCorners = 3000,
qualityLevel = 0.5,
minDistance = 3,
blockSize = 3)
def lk():
cam = cv2.VideoCapture(0)
_, img = cam.read()
oldg = cv2.cvtColor(img, cv2.cv.CV_BGR2GRAY)
bb = [200,200,300,300]
old_pts=[]
while True:
try:
_, img = cam.read()
img1 = img[bb[0]:bb[2],bb[1]:bb[3]]
#print img1.shape
g = cv2.cvtColor(img1, cv2.cv.CV_BGR2GRAY)
#print g.shape
pt = cv2.goodFeaturesToTrack(g, **feature_params)
for i in xrange(len(pt)):
pt[i][0][0] = pt[i][0][0]+bb[0]
pt[i][0][1] = pt[i][0][1]+bb[1]
newg = cv2.cvtColor(img, cv2.cv.CV_BGR2GRAY)
p0 = np.float32(pt).reshape(-1, 1, 2)
p1, st, err = cv2.calcOpticalFlowPyrLK(oldg, newg, p0, None, **lk_params)
p0r, st, err = cv2.calcOpticalFlowPyrLK(newg, oldg, p1, None, **lk_params)
d = abs(p0-p0r).reshape(-1, 2).max(-1)
good = d < 1
new_pts = []
for pts, val in itertools.izip(p1, good):
if val:
new_pts.append([pts[0][0], pts[0][1]])
cv2.circle(img, (pts[0][0], pts[0][1]), 5, thickness=3, color=(255,255,0))
bb = predictBB(bb, old_pts, new_pts)
if bb[0]+bb[2] >= img.shape[0]:
bb[0] = img.shape[0] - bb[2] - 1
if bb[1]+bb[3] >= img.shape[1]:
bb[1] = img.shape[1] - bb[3] - 1
old_pts = new_pts
oldg = newg
cv2.rectangle(img, (bb[0],bb[1]),(bb[0]+bb[2],bb[1]+bb[3]), color=(255,0,0))
cv2.imshow("LK", img)
cv2.waitKey(1)
except KeyboardInterrupt:
break
def predictBB(bb0, pt0, pt1):
if not pt0:
pt0 = pt1
dx=[]
dy=[]
for p1, p2 in itertools.izip(pt0, pt1):
dx.append(p2[0]-p1[0])
dy.append(p2[1]-p1[1])
if not dx or not dy:
return bb0
cen_dx = round(sum(dx)/len(dx))
cen_dy = round(sum(dy)/len(dy))
print cen_dx, cen_dy,
print "shift"
bb = [int(bb0[0]+cen_dx), int(bb0[1]+cen_dy), int(bb0[2]), int(bb0[3])]
if bb[0] <= 0:
bb[0] = 1
if bb[1] <= 0:
bb[1] = 1
return bb
lk()
@MatKallada

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MatKallada commented Oct 22, 2013

Hey Jay,

I seem to get this issue,

0.0 0.0 shift
-20.0 14.0 shift
-18.0 30.0 shift
-35.0 17.0 shift
-44.0 18.0 shift
-58.0 97.0 shift

Traceback (most recent call last):
File "/media/mathew/d19f4260-bc8b-44b2-9209-1ed9bde9abfd/home/mat/Desktop/dddd.py", line 75, in
lk()
File "/media/mathew/d19f4260-bc8b-44b2-9209-1ed9bde9abfd/home/mat/Desktop/dddd.py", line 28, in lk
for i in xrange(len(pt)):
TypeError: object of type 'NoneType' has no len()

@Biri-Biri-Chan

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Biri-Biri-Chan commented Jun 4, 2015

I have the same error

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