draw a circle over image opencv

Question

Im usign python and opencv to get a image from the webcam, and I want to know how to draw a circle over my image, just a simple green circle with transparent fill

Answer 1

cv2.circle(img, center, radius, color, thickness=1, lineType=8, shift=0) → None
Draws a circle.

Parameters: 
img (CvArr) – Image where the circle is drawn
center (CvPoint) – Center of the circle
radius (int) – Radius of the circle
color (CvScalar) – Circle color
thickness (int) – Thickness of the circle outline if positive, otherwise this indicates that a filled circle is to be drawn
lineType (int) – Type of the circle boundary, see Line description
shift (int) – Number of fractional bits in the center coordinates and radius value

Use "thickness" parameter for only the border.