从圆绘制圆和线段答案

【问题标题】：Draw circle and segments from circle从圆绘制圆和线段
【发布时间】：2015-10-20 17:25:12
【问题描述】：

我想画一个圆圈并从这个圆圈中画出线段。抱歉，因为我在 stackoverflow 上找到了很多主题，但是仍然没有人可以帮助我完全理解。你能给我一个示例代码吗？我想要如下图所示的结果。非常感谢

【问题讨论】：

【解决方案1】：

打开一个新的 Swift 3 Playground 并将以下代码粘贴到其中。您应该会在右侧看到“w 512 h 512”注释，点击它会出现一只眼睛。那时你应该会看到一些图画。

    //: Playground - noun: a place where people can play
import UIKit
import CoreGraphics

public func makePieChart()-> UIImage?
{
    let size = CGSize(width: 512, height:512)
    let centerX = size.width/2.0
    let centerY = size.height/2.0
    let center = CGPoint(x: centerX, y: centerY)
    let chartRadius = size.width/2.0

    UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
    defer
    {
        UIGraphicsEndImageContext()
    }


    guard let quartz = UIGraphicsGetCurrentContext() else
    {
        return nil
    }
    let π = CGFloat.pi

    quartz.move(to: center)
    quartz.addArc(center: center, radius: chartRadius, startAngle: 0.0, endAngle: π/3.0, clockwise: false)
    quartz.closePath() // path will complete back at the last move to (center of the circle)

    quartz.setFillColor(UIColor.red.cgColor)
    quartz.fillPath()


    quartz.move(to: center)
    quartz.addArc(center: center, radius: chartRadius, startAngle:  π/3.0, endAngle: π, clockwise: false)

    quartz.closePath() // path will complete back at the last move to (center of the circle)

    quartz.setFillColor(UIColor.yellow.cgColor)
    quartz.fillPath()
    quartz.move(to: center)
    quartz.addArc(center: center, radius: chartRadius, startAngle:  π, endAngle: 0.0, clockwise: false)

    quartz.closePath() // path will complete back at the last move to (center of the circle)

    quartz.setFillColor(UIColor.blue.cgColor)
    quartz.fillPath()
    return UIGraphicsGetImageFromCurrentImageContext()
}

let image = makePieChart()

【讨论】：