前言:

绘制内阴影，原作者地址：https://www.jianshu.com/p/b4d1a0b6439a

发现了一个大师写的内阴影代码，挺好用的，但是直接复制粘贴有报错，我修改了下报错。

效果图：

内阴影.PNG

上代码！

WLInnerShadow.swift

import UIKit

class WLInnerShadow: CAShapeLayer {
    
    var innerShadowColor: CGColor? = UIColor.black.cgColor {
        didSet { setNeedsDisplay() }
    }
    
    var innerShadowOffset: CGSize = CGSize(width: 0, height: 0) {
        didSet { setNeedsDisplay() }
    }
    
    var innerShadowRadius: CGFloat = 8 {
        didSet { setNeedsDisplay() }
    }
    
    var innerShadowOpacity: Float = 1 {
        didSet { setNeedsDisplay() }
    }
    
    override init() {
        super.init()
        initialize()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initialize()
    }
    
    func initialize() {
        self.masksToBounds      = true
        self.shouldRasterize    = true
        self.contentsScale      = UIScreen.main.scale
        self.rasterizationScale = UIScreen.main.scale
        
        setNeedsDisplay()
    }
    
    override func draw(in ctx: CGContext) {
        // 设置 Context 属性
        // 允许抗锯齿
        //CGContextSetAllowsAntialiasing(ctx, true);
        ctx.setAllowsAntialiasing(true)
        // 允许平滑
        //CGContextSetShouldAntialias(ctx, true);
        ctx.setShouldAntialias(true)
        // 设置插值质量
        //CGContextSetInterpolationQuality(ctx, .High);
        ctx.interpolationQuality = .high
        
        // 以下为核心代码
        
        // 创建 color space
        let colorspace = CGColorSpaceCreateDeviceRGB();
        
        var rect   = self.bounds
        var radius = self.cornerRadius
        
        // 去除边框的大小
        if self.borderWidth != 0 {
            //rect   = CGRectInset(rect, self.borderWidth, self.borderWidth);
            rect   = rect.insetBy(dx: borderWidth, dy: borderWidth)
            radius -= self.borderWidth
            radius = max(radius, 0)
        }
        
        // 创建 inner shadow 的镂空路径
        let someInnerPath: CGPath = UIBezierPath(roundedRect: rect, cornerRadius: radius).cgPath
        ctx.addPath(someInnerPath)
        ctx.clip()
        
        // 创建阴影填充区域，并镂空中心
        
        let shadowPath = CGMutablePath()
        //let shadowRect = CGRectInset(rect, -rect.size.width, -rect.size.width)
        let shadowRect = rect.insetBy(dx: -rect.size.width, dy: -rect.size.width)
        
        //CGPathAddRect(shadowPath, nil, shadowRect)
        shadowPath.addRect(shadowRect)
        
        //CGPathAddPath(shadowPath, nil, someInnerPath);
        shadowPath.addPath(someInnerPath)
        
        //CGPathCloseSubpath(shadowPath)
        shadowPath.closeSubpath()
        
        
        // 获取填充颜色信息
        //let oldComponents: UnsafePointer<CGFloat> = CGColorGetComponents(innerShadowColor)
        let oldComponents = innerShadowColor?.components ?? [0, 0, 0, 0]
        
        var newComponents:[CGFloat] = [0, 0, 0, 0]
        
        //let numberOfComponents: Int = CGColorGetNumberOfComponents(innerShadowColor);
        let numberOfComponents = innerShadowColor?.numberOfComponents
        
        switch (numberOfComponents){
        case 2:
            // 灰度
            newComponents[0] = oldComponents[0]
            newComponents[1] = oldComponents[0]
            newComponents[2] = oldComponents[0]
            newComponents[3] = oldComponents[1] * CGFloat(innerShadowOpacity)
        case 4:
            // RGBA
            newComponents[0] = oldComponents[0]
            newComponents[1] = oldComponents[1]
            newComponents[2] = oldComponents[2]
            newComponents[3] = oldComponents[3] * CGFloat(innerShadowOpacity)
        default: break
        }
        
        // 根据颜色信息创建填充色
        //let innerShadowColorWithMultipliedAlpha = CGColorCreate(colorspace, newComponents)
        let innerShadowColorWithMultipliedAlpha = CGColor(colorSpace: colorspace, components: &newComponents) ?? UIColor.black.cgColor
        
        // 填充阴影
        //CGContextSetFillColorWithColor(ctx, innerShadowColorWithMultipliedAlpha)
        ctx.setFillColor(innerShadowColorWithMultipliedAlpha)
        
        //CGContextSetShadowWithColor(ctx, innerShadowOffset, innerShadowRadius, innerShadowColorWithMultipliedAlpha)
        ctx.setShadow(offset: innerShadowOffset, blur: innerShadowRadius, color: innerShadowColorWithMultipliedAlpha)
        
        //CGContextAddPath(ctx, shadowPath)
        ctx.addPath(shadowPath)
        
        //CGContextEOFillPath(ctx)
        ctx.fillPath(using: .evenOdd)
    }
}

使用示例：

import UIKit

class InnerShadowViewController_3: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let myView                      = UIView(frame: CGRect(x: 0, y: 0, width: 280, height: 280))
        myView.layer.backgroundColor    = UIColor.init(hex: 0xeeeeee).cgColor
        myView.center                   = self.view.center
        myView.layer.cornerRadius       = myView.bounds.size.width / 2
        myView.layer.shouldRasterize    = true
        myView.layer.contentsScale      = UIScreen.main.scale
        myView.layer.rasterizationScale = UIScreen.main.scale
                
        let shadowLayer                = WLInnerShadow()
        shadowLayer.frame              = myView.bounds
        shadowLayer.cornerRadius       = myView.layer.cornerRadius
        shadowLayer.innerShadowOffset  = CGSize(width: 4, height: 4)
        shadowLayer.innerShadowOpacity = 0.5
        shadowLayer.innerShadowRadius  = 16
        myView.layer.addSublayer(shadowLayer)
                
        self.view.addSubview(myView)

    }
}

结语

这个可以设置透明度了。