I get this result when fitting an ellipse to a contour (the contour is green, the fitted ellipse in blue)

Here's the original image :

Why doesn't it fit? Here is the code :

img1 = cv2.imread(r'limb_edge_fl28_iss3628.jpg')

gray1 = cv2.cvtColor(img1, cv2.COLOR_BGR2GRAY)

Threshold the images

thresh1 = cv2.threshold(gray1, 127, 255, cv2.THRESH_BINARY)[1]

contours = cv2.findContours(thresh1.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)[1]

cnt1 = contours[0]

draw contours found

cv2.drawContours(img1, [cnt1], 0, green, 2)

Fit an ellipse to the contours

ellipse = cv2.fitEllipse(cnt1)

Draw the ellipse on the image

cv2.ellipse(img1,ellipse,(255,255,0),2)

cv2.imshow("ellipse fit 1", img1)

I get this result when fitting an ellipse to a contour (the contour is green, the fitted ellipse in blue)

Here's the original image : :

Why doesn't it fit?

Here is the code :

----------
img1 = cv2.imread(r'limb_edge_fl28_iss3628.jpg')
cv2.imread(r'limb_edge_fl28_iss3628.jpg')
  
gray1 = cv2.cvtColor(img1, cv2.COLOR_BGR2GRAY)cv2.COLOR_BGR2GRAY)
  
# Threshold the images
 
images
thresh1 = cv2.threshold(gray1, 127, 255, cv2.THRESH_BINARY)[1]cv2.THRESH_BINARY)[1]
  
contours = cv2.findContours(thresh1.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)[1]cv2.CHAIN_APPROX_NONE)[1]
  
cnt1 = contours[0]contours[0]
  
# draw contours found
 
found
cv2.drawContours(img1, [cnt1], 0, green, 2)2)
  
# Fit an ellipse to the contourscontours
ellipse = cv2.fitEllipse(cnt1)
 
ellipse = cv2.fitEllipse(cnt1)
 
# Draw the ellipse on the imageimage
cv2.ellipse(img1,ellipse,(255,255,0),2)
  
cv2.ellipse(img1,ellipse,(255,255,0),2)
 
cv2.imshow("ellipse fit 1", img1)img1)