Search code examples
iosswiftcore-graphics

How can I draw line intersecting the arc perpendicularly(Core Graphics)?

I want to draw a line on the circle(intercepting the arc of the circle) perpendicularly like in the picture.

I am using this code to draw circle

let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)

let path = UIBezierPath(arcCenter: center, radius: radius, startAngle: Conversion.degreesToRadians(value: CGFloat(0)), endAngle: Conversion.degreesToRadians(value: CGFloat(360)), clockwise: true)
path.lineWidth = 2
path.lineCapStyle = CGLineCap.square
UIColor.white.setStroke()
path.stroke()

enter image description here

Solution

  • The basic idea is that a circle has a certain radius about a center CGPoint. To figure out a point on the circle, you can calculate the x and y coordinates like so:

    func point(center: CGPoint, radius: CGFloat, angle: CGFloat) -> CGPoint {
    let x = center.x + radius * cos(angle)
    let y = center.y + radius * sin(angle)
    return CGPoint(x: x, y: y)
}

    where the angle is measured in radians, starting at 3 o'clock and going clockwise.

    So those perpendicular intersecting strokes are merely line segments between two CGPoint at a given angle, where the "radius" used for the start of the line segment might be, for example, something just less than the radius of the circle. For the ending point of the line, use the same angle, but then use a radius value just greater than the radius of the circle.