CODEWITHSUNDEEP
pythonopencvtrackingopticalflow
Froyo
Froyo

Reputation: 18477

TypeError: <unknown> is not a numpy array in cv2.calcOpticalFlowPyrLK()

I'm trying to make an LK tracker in OpenCV 2.3.1 with python bindings. When I do

calcOpticalFlowPyrLK(img1, img2,
                   template_pt, target_pt, status, err, 
                   (win_size_lk, win_size_lk), 0, TERM_CRITERIA_EPS, 
                   (TERM_CRITERIA_EPS | TERM_CRITERIA_COUNT, 10, 0.03), eig)

I'm getting

TypeError: is not a numpy array

where

img1, img2 - iplimage
template_pt, target_pt - A List consisting of tuples with two integers eg. [(120,140),(300,400),..]
win_size_lk = 10
eig = 0.001
status = ""
err = None

More info about cv2.calcOpticalFlowPyrLK() is given here

http://opencv.itseez.com/modules/video/doc/motion_analysis_and_object_tracking.html?highlight=opticalflow#cv.CalcOpticalFlowPyrLK

When I set

eig = np.array([(0.0,1.0),(1.0,0.0)])

It gives me the following error

TypeError: only length-1 arrays can be converted to Python scalars

What could be the problem here ?

Upvotes: 2

Views: 3443

Answers (1)

Froyo
Froyo

Reputation: 18477

I have figured out the problem. 

img1, img2 should be numpy array
template_pt, target_pt should be numpy array

So,

target_pt, status, track_error = calcOpticalFlowPyrLK(img1, 
                  img2, 
                  template_pt, 
                  target_pt, 
                  winSize=(win_size_lk, win_size_lk), 
                  flags = OPTFLOW_USE_INITIAL_FLOW,
                  criteria = (TERM_CRITERIA_EPS | TERM_CRITERIA_COUNT, 10, 0.03))

works well.

Upvotes: 1

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