How to track white color on black background

asked 2015-07-22 02:54:34 -0500

mmt gravatar image

I have a code that doesn't works to white and black color.

On the code I select the ROI, and after that this code is supposed to keep tracking the ball, but it doesn't happen

I have this video :

and this code :

import numpy as np
import cv2

cap = cv2.VideoCapture('video.avi')

ret,frame =

r,h,c,w = 490,50,895,50  # It is where the ball is.  
track_window = (c,r,w,h)
frame = cv2.cvtColor(frame, cv2.COLOR_GRAY2BGR)

roi = frame[r:r+h, c:c+w]
hsv_roi =  cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
mask = cv2.inRange(hsv_roi, np.array((0., 60.,32.)), np.array((180.,255.,255.)))
roi_hist = cv2.calcHist([hsv_roi],[0],mask,[180],[0,180])

term_crit = ( cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 1 )

    ret ,frame =

    if ret == True:
        hsv = cv2.cvtColor(frame, cv2.COLOR_BGR2HSV)
        dst = cv2.calcBackProject([hsv],[0],roi_hist,[0,180],1)

        ret, track_window = cv2.meanShift(dst, track_window, term_crit)

        x,y,w,h = track_window
        img2 = cv2.rectangle(frame, (x,y), (x+w,y+h), 255,2)

        k = cv2.waitKey(60) & 0xff
        if k == 27:



I have no clue about what should I do, I tried to convert from gray to bgr, but it didn't works.

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you need color input for camshift algorithm. it will just never work with grayscale or b/w

(and the conversion only makes 3 identical channels, so nothing gained from that, in the end, you can't get the color information back, once it was lost)

if you must work on b/w data, you will need a different tracking algorithm, maybe the mosse tracker works better there.

berak gravatar imageberak ( 2015-07-22 03:07:07 -0500 )edit

Thank you for this information! I was going crazy with that code! I will try this one and update you! Thanks!

mmt gravatar imagemmt ( 2015-07-22 03:35:58 -0500 )edit

Is there a mosse tracker for C++, or it is just for python?

thdrksdfthmn gravatar imagethdrksdfthmn ( 2015-07-22 07:09:04 -0500 )edit

just for python, afaaik.

berak gravatar imageberak ( 2015-07-22 07:14:52 -0500 )edit