Drawing 2D Graphics in iOS Swift

In this I'll explain how to draw 2D graphics using Core Graphics in iOS Swift. We will use Quardz 2D API. 

Quardz 2D is low level light-weight 2D rendring and drawing engine.It is based on coordinate system (0,0) represent the device top left corner. In iOS CGPoint  (a structure) is used to specify a point. similarly rectangle can be defined by CGRect structure.

Graphics Context :  View has a graphic context which is responsible for drawing requests, so to draw on device screen we need graphics context of view. so  to graphics context we've to call UIGraphicsGetCurrentContext() which return CGContextRef.

let contextRef = UIGraphicsGetCurrentContext()

Drawing Paths : For drawing we've to subclass a UIView class.

import UIKit
class Draw2D: UIView { 
override func draw(_ rect: CGRect) { 
let context = UIGraphicsGetCurrentContext()
context?.setLineWidth(2.0)
context?.setStrokeColor(UIColor.blue.cgColor)
context?.move(to: CGPoint(x:100, y: 100))
context?.addLine(to: CGPoint(x: 150, y: 150))
context?.addLine(to: CGPoint(x: 100, y: 200))
context?.addLine(to: CGPoint(x: 50, y: 150))
context?.addLine(to: CGPoint(x: 100, y: 100))
context?.strokePath()
}
}

Filling Paths with Color :  For filling the paths we'll use cgColor property of UIColor class.

context?.setFillColor(UIColor.red.cgColor) context?.fillPath()

Drawing Qurardatic Beizer curve :  Instead of addLine function we'll add addQuadCurve function to draw curves.

context?.addQuadCurve(to: CGPoint(x: 300, y: 200),   control: CGPoint(x: 150, y: 10))

Thanks