cv2.ellipse() method - Python OpenCV

cv2.ellipse() method in OpenCV is used to draw an ellipse on an image. It allows you to control the ellipse’s position, size, rotation, color and thickness making it useful for highlighting regions, marking detected objects or creating shapes in image processing tasks.

Note: For this article we will use a sample image "logo.png", to download click here.

Example: This example loads an image and draws a red ellipse with no rotation using minimal parameters.

Python

import cv2

img = cv2.imread("logo.png")

center = (120, 100)
axes = (80, 40)
img = cv2.ellipse(img, center, axes, 0, 0, 360, (0, 0, 255), 3)

cv2.imshow("Ellipse", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output

Explanation:

cv2.ellipse(img, center, axes, ...): draws the ellipse on the image
center: position of the ellipse
axes: lengths of major & minor axes
0, 0, 360: no rotation, full ellipse
(0, 0, 255): red color (BGR)
3: border thickness

Syntax

cv2.ellipse(image, center, axes, angle, startAngle, endAngle, color, thickness)

Parameters:

image: Image on which ellipse is drawn.
center: Center of ellipse as (x, y).
axes: Tuple (major axis, minor axis) lengths.
angle: Rotation of ellipse in degrees.
startAngle: Starting angle of arc.
endAngle: Ending angle of arc.
color: BGR color tuple.
thickness: Border thickness (-1 fills the ellipse).

Example 1: This example draws a filled blue ellipse with no rotation.

Python

import cv2

img = cv2.imread("logo.png")

center = (100, 80)
axes = (70, 40)

img = cv2.ellipse(img, center, axes, 0, 0, 360, (255, 0, 0), -1)

cv2.imshow("Ellipse 1", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output

Explanation:

-1: fills the ellipse
(255, 0, 0): blue color
0 rotation: straight ellipse

Example 2: This example draws a rotated green ellipse at 45 degrees.

Python

import cv2

img = cv2.imread("logo.png")

center = (150, 120)
axes = (90, 50)

img = cv2.ellipse(img, center, axes, 45, 0, 360, (0, 255, 0), 4)

cv2.imshow("Ellipse 2", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output

Explanation:

45: rotates ellipse
(0, 255, 0): green color
4: thicker border

Example 3: This example draws a partial red arc (not a full ellipse).

Python

import cv2

img = cv2.imread("logo.png")

center = (120, 100)
axes = (100, 60)

img = cv2.ellipse(img, center, axes, 0, 0, 180, (0, 0, 255), 3)

cv2.imshow("Ellipse 3", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output

Explanation:

0, 180: draws only half ellipse
(0, 0, 255): red arc
3: border thickness

cv2.ellipse() method - Python OpenCV

Syntax

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