Tracking a white ball in a white background (Python / OpenCV)
I am using OpenCV in Python 3 to define a white / black ball on a white field and give it accurate (x, y, radius) and color.
I use the cv2.Canny () and cv2.findContours () function to find it, but the problem in cv2.Canny () doesn't always detect the full circle shape (most of the time only 3/4 of the circle). So when I use cv2.findContours () it doesn't define it as Contour.
Please look:
and 
This is the most important code:
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
blurred = cv2.GaussianBlur(gray, (5, 5), 0)
edged = cv2.Canny(blurred, 10, 40) # 10 and 40 to be more perceptive
contours_canny= cv2.findContours(edged.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)[-2]
After that I use:
approx = cv2.approxPolyDP(contour,0.01*cv2.arcLength(contour,True),True)
So, if you can help me find a solution, that would be great! Maybe there is a function that completes the circle shape so I can detect it?
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I would suggest that you apply some intermediate color filtering before using canny detection. This ensures that canny edge detection occurs at a well-defined border between the ball image and the field.
Here is the python code that uses the trackballs so you can adjust the color threshold:
cv2.namedWindow('temp')
cv2.createTrackbar('bl', 'temp', 0, 255, nothing)
cv2.createTrackbar('gl', 'temp', 0, 255, nothing)
cv2.createTrackbar('rl', 'temp', 0, 255, nothing)
cv2.createTrackbar('bh', 'temp', 255, 255, nothing)
cv2.createTrackbar('gh', 'temp', 255, 255, nothing)
cv2.createTrackbar('rh', 'temp', 255, 255, nothing)
bl_temp=cv2.getTrackbarPos('bl', 'temp')
gl_temp=cv2.getTrackbarPos('gl', 'temp')
rl_temp=cv2.getTrackbarPos('rl', 'temp')
bh_temp=cv2.getTrackbarPos('bh', 'temp')
gh_temp=cv2.getTrackbarPos('gh', 'temp')
rh_temp=cv2.getTrackbarPos('rh', 'temp')
thresh=cv2.inRange(frame,(bl_temp,gl_temp,rl_temp),(bh_temp,gh_temp,rh_temp))
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