Added a Swift implementation of SiriWaveformView

SCSiriWaveformView/SiriWaveformView.swift

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+//
+//  SiriWaveformView.swift
+//  SiriWaveformView
+//
+//  Created by Matheus Felizola Freires on 20/07/17.
+//  Original Objective-C code by Stefan Ceriu https://github.com/stefanceriu/SCSiriWaveformView
+//
+//  Copyright © 2017 BEPiD. All rights reserved.
+//
+
+import UIKit
+
+@IBDesignable class SiriWaveformView: UIView {
+    var phase: CGFloat = 0
+    @IBInspectable var amplitude: CGFloat = 1
+    @IBInspectable var numberOfWaves:Int = 5
+    @IBInspectable var waveColor: UIColor = .white
+    @IBInspectable var primaryWaveLineWidth: CGFloat = 5
+    @IBInspectable var secondaryWaveLineWidth: CGFloat = 1
+    @IBInspectable var idleAmplitude: CGFloat = 0.01
+    @IBInspectable var frequency: CGFloat = 1.5
+    @IBInspectable var density: CGFloat = 5
+    @IBInspectable var phaseShift: CGFloat = -0.15
+
+    func updateWithLevel(_ level: CGFloat) {
+        self.phase += self.phaseShift
+        self.amplitude = fmax(level, self.idleAmplitude)
+
+        self.setNeedsDisplay()
+    }
+
+    //Thanks to Raffael Hannemann https://github.com/raffael/SISinusWaveView
+    override func draw(_ rect: CGRect) {
+        if let context = UIGraphicsGetCurrentContext() {
+            context.clear(self.bounds)
+            self.backgroundColor?.set()
+            context.fill(rect)
+
+            //We draw multiple sinus waves, with equal phases but altered amplitudes, multiplied by a parable function.
+            for i in 0...self.numberOfWaves {
+                let strokeLineWidth = i == 0 ? self.primaryWaveLineWidth : self.secondaryWaveLineWidth
+                context.setLineWidth(strokeLineWidth)
+
+                let halfHeight = self.bounds.height / 2
+                let width = self.bounds.width
+                let mid = width / 2
+
+                let maxAmplitude = halfHeight - strokeLineWidth*2
+
+                let progress:CGFloat = CGFloat(1 - i / self.numberOfWaves)
+                let normedAmplitude = (1.5 * progress - CGFloat(2 / self.numberOfWaves)) * self.amplitude
+
+                let multiplier = min(1, (progress / 3*2) + (1/3))
+                self.waveColor.withAlphaComponent(multiplier*self.waveColor.cgColor.alpha).set()
+                for x in stride(from: 0, to: width+self.density, by: self.density) {
+                    //We use a parable to scale the sinus wave, that has it's peak in the middle of the view.
+                    let scaling = 1 - pow(1/mid*(x-mid), 2)
+                    let y = scaling * maxAmplitude * normedAmplitude * CGFloat(sinf(Float(2 * .pi * x/width * self.frequency + self.phase))) + halfHeight
+
+                    if(x==0) {
+                        context.move(to: CGPoint(x: x, y: y))
+                    } else {
+                        context.addLine(to: CGPoint(x: x, y: y))
+                    }
+                }
+
+                context.strokePath()
+            }
+        }
+    }
+}