Draws a simple or thick elliptic arc or fills an ellipse sector

img = cv.ellipse(img, center, axes)
img = cv.ellipse(img, box)
[...] = cv.ellipse(..., 'OptionName', optionValue, ...)

Input

• img Image where the ellipse is drawn.
• center Center of the ellipse [x,y].
• axes Half of the size of the ellipse main axes [a,b].
• box Alternative ellipse representation via a rotated rectangle box. This means that the function draws an ellipse inscribed in the rotated rectangle. A scalar structure with the following fields:
  • center The rectangle mass center [x,y].
  • size Width and height of the rectangle [w,h].
  • angle The rotation angle in a clockwise direction. When the angle is 0, 90, 180, 270 etc., the rectangle becomes an up-right rectangle.

Output

• img Output image, same size and type as input img.

Options

• Angle Ellipse rotation angle in degrees. default 0.
• StartAngle Starting angle of the elliptic arc in degrees. default 0
• EndAngle Ending angle of the elliptic arc in degrees. default 360
• Color 3-element floating-point vector specifying ellipse color.
• Thickness Thickness of the ellipse arc outline, if positive. Otherwise, this indicates that a filled ellipse sector is to be drawn (-1 or the string 'Filled'). default 1.
• LineType Type of the ellipse boundary. One of:
  • 4 4-connected line
  • 8 8-connected line (default)
  • AA anti-aliased line
• Shift Number of fractional bits in the coordinates of the center and values of axes. default 0.

The first variant of the cv.ellipse function draws an ellipse outline, a filled ellipse, an elliptic arc, or a filled ellipse sector. The drawing code uses general parametric form. A piecewise-linear curve is used to approximate the elliptic arc boundary. If you need more control of the ellipse rendering, you can retrieve the curve using cv.ellipse2Poly and then render it with cv.polylines or fill it with cv.fillPoly. If you use the first variant of the function and want to draw the whole ellipse, not an arc, pass StartAngle=0 and EndAngle=360. If StartAngle is greater than EndAngle, they are swapped. The figure below explains the meaning of the parameters to draw the blue arc.

The second variant of the function (with rotated rectange as input) does not support the Angle, StartAngle, EndAngle, and Shift parameters (always draw a whole ellipse, not an arc).