I have a webcam feed using OpenCV, and I am trying to fit an ellipse in real time.
The code I am using at the moment works, but it fails to fit an ellipse to the image a lot of the time. What other methods of ellipse fitting to an image can I pursue?
Current code:
def find_ellipses(img): #img is grayscale image of what I want to fit
ret,thresh = cv2.threshold(img,127,255,0)
_,contours,hierarchy = cv2.findContours(thresh, 1, 2)
if len(contours) != 0:
for cont in contours:
if len(cont) < 5:
break
elps = cv2.fitEllipse(cont)
return elps #only returns one ellipse for now
return None
Where elps
is of the form (x_centre,y_centre),(minor_axis,major_axis),angle
Here is an example of what I want to successfully fit an ellipse to. My current code fails with this image when I don't want it to.
Turns out I was wrong is just getting the first ellipse from the function. While I thought the first calculated ellipse was the most correct one, what I actually had to do was go through all the ellipses - and choose the most suitable one that bounded the object in the image.
I would define my contours outside of the function, as you don't need to keep re-defining them in this image.
def create_ellipse(thresh,cnt):
ellipse = cv2.fitEllipse(cnt)
thresh = cv2.ellipse(thresh,ellipse,(0,255,0),2)
return thresh
What this code is doing is im taking my thresh image stream and adding an ellipse on top of it. Later on in my code when I want to call it I use the line
thresh = create_ellipse(thresh,cnt)
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