如何将 CAGradientLayer 添加到 CAShapeLayer？

Question

我正在尝试将 CAGradientLayer 添加到 CAShapeLayer，但渐变不符合图层的形状。相反，渐变采用 UIView 本身的形状。我最初尝试使用 UIBezierPath 进行此操作，但它也不起作用。我正在尝试在我的形状中添加渐变。

  override func drawRect(rect: CGRect) {
        let bounds = CGRect(x: 0, y: 0, width: self.bounds.width, height: self.bounds.height)
        let center = self.center

        let path = CAShapeLayer()
        path.bounds = bounds
        path.position = CGPoint(x: center.x, y: center.y)
        //path.backgroundColor = UIColor.redColor().CGColor
        path.cornerRadius = 20
        //self.layer.addSublayer(path)
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = path.bounds
        gradientLayer.colors = [cgColorForRed(209.0, green: 0.0, blue: 0.0),
            cgColorForRed(255.0, green: 102.0, blue: 34.0),
            cgColorForRed(255.0, green: 218.0, blue: 33.0),
            cgColorForRed(51.0, green: 221.0, blue: 0.0),
            cgColorForRed(17.0, green: 51.0, blue: 204.0),
            cgColorForRed(34.0, green: 0.0, blue: 102.0),
            cgColorForRed(51.0, green: 0.0, blue: 68.0)]
        gradientLayer.startPoint = CGPoint(x:0,y:0)
        gradientLayer.endPoint = CGPoint(x:0, y:1)
        path.insertSublayer(gradientLayer, atIndex: 1)
        self.layer.addSublayer(path)


    }

    func cgColorForRed(red: CGFloat, green: CGFloat, blue: CGFloat ) -> AnyObject {
        return UIColor(red: red/255.0, green: green/255.0, blue: blue/255.5, alpha: 1.0).CGColor as AnyObject
    }

最初我将路径定义为带有圆角的矩形的 UIBezierPath，我希望用渐变填充它：

        let insetRect = CGRectInset(rect, lineWidth / 2, lineWidth / 2)

        let path = UIBezierPath(roundedRect: insetRect, cornerRadius: 10)

        fillColor.setFill()
        path.fill()

        path.lineWidth = self.lineWidth
        UIColor.blackColor().setStroke()
        path.stroke()

根据 Larcerax 的回复编辑：

class Thermometer: UIView {

    //@IBInspectable var fillColor: UIColor = UIColor.greenColor()
    let lineWidth: CGFloat = 2

    override func drawRect(rect: CGRect) {

        let context = UIGraphicsGetCurrentContext()
        let svgid = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), [cgColorForRed(209.0, green: 0.0, blue: 0.0),
            cgColorForRed(255.0, green: 102.0, blue: 34.0),
            cgColorForRed(255.0, green: 218.0, blue: 33.0),
            cgColorForRed(51.0, green: 221.0, blue: 0.0),
            cgColorForRed(17.0, green: 51.0, blue: 204.0),
            cgColorForRed(34.0, green: 0.0, blue: 102.0),
            cgColorForRed(51.0, green: 0.0, blue: 68.0)], [0,1])
        CGContextSaveGState(context)
        let insetRect = CGRectInset(rect, lineWidth / 2, lineWidth / 2)

        let path = UIBezierPath(roundedRect: insetRect, cornerRadius: 10)
        path.addClip()
        CGContextDrawLinearGradient(context, svgid, CGPoint(x: 0, y: path.bounds.height),
            CGPoint(x: path.bounds.width, y: path.bounds.height),
            UInt32(kCGGradientDrawsBeforeStartLocation) | UInt32(kCGGradientDrawsAfterEndLocation))
        CGContextRestoreGState(context)
}

Answer 1

您可以尝试以下设置以生成以下形状，这只是向您展示设置的示例，但应该这样做：

    let context = UIGraphicsGetCurrentContext()

    let gradientColor3 = UIColor(red: 1.000, green: 1.000, blue: 1.000, alpha: 1.000)
    let gradientColor4 = UIColor(red: 0.000, green: 1.000, blue: 0.000, alpha: 1.000)

    let sVGID_1_2 = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), [gradientColor3.CGColor, gradientColor4.CGColor], [0, 1])

    CGContextSaveGState(context)
    CGContextTranslateCTM(context, 198.95, 199.4)
    CGContextRotateCTM(context, -30 * CGFloat(M_PI) / 180)

    var polygonPath = UIBezierPath()
    polygonPath.moveToPoint(CGPointMake(0, -145.95))
    polygonPath.addLineToPoint(CGPointMake(126.4, -72.98))
    polygonPath.addLineToPoint(CGPointMake(126.4, 72.97))
    polygonPath.addLineToPoint(CGPointMake(0, 145.95))
    polygonPath.addLineToPoint(CGPointMake(-126.4, 72.98))
    polygonPath.addLineToPoint(CGPointMake(-126.4, -72.97))
    polygonPath.closePath()
    CGContextSaveGState(context)
    polygonPath.addClip()
    CGContextDrawLinearGradient(context, sVGID_1_2,
        CGPointMake(-126.4, -72.97),
        CGPointMake(126.41, 72.99),
        UInt32(kCGGradientDrawsBeforeStartLocation) | UInt32(kCGGradientDrawsAfterEndLocation))
    CGContextRestoreGState(context)

制作这个：

如果这不起作用，请告诉我，我会尝试修复它以使其正常工作。

另外，这里只是一个简单的矩形：

let context = UIGraphicsGetCurrentContext()

let gradientColor = UIColor(red: 1.000, green: 1.000, blue: 1.000, alpha: 1.000)
let gradientColor2 = UIColor(red: 0.988, green: 0.933, blue: 0.129, alpha: 1.000)
let gradientColor3 = UIColor(red: 1.000, green: 0.000, blue: 1.000, alpha: 1.000)

let sVGID_1_3 = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), [gradientColor.CGColor, gradientColor2.CGColor, gradientColor3.CGColor], [0, 0.43, 1])

let rectanglePath = UIBezierPath(rect: CGRectMake(68, 28, 78.4, 78.4))
CGContextSaveGState(context)
rectanglePath.addClip()
CGContextDrawLinearGradient(context, sVGID_1_3,
    CGPointMake(68, 67.19),
    CGPointMake(146.38, 67.19),
    UInt32(kCGGradientDrawsBeforeStartLocation) | UInt32(kCGGradientDrawsAfterEndLocation))
CGContextRestoreGState(context)

这里有一个功能可以尝试，你必须弄乱颜色，但你可以输入一个框架：

class func drawStuff(#frame: CGRect) {
        let context = UIGraphicsGetCurrentContext()

        let gradientColor = UIColor(red: 1.000, green: 1.000, blue: 1.000, alpha: 1.000)
        let gradientColor2 = UIColor(red: 0.988, green: 0.933, blue: 0.129, alpha: 1.000)
        let gradientColor3 = UIColor(red: 1.000, green: 0.000, blue: 1.000, alpha: 1.000)

        let sVGID_1_4 = CGGradientCreateWithColors(CGColorSpaceCreateDeviceRGB(), [gradientColor.CGColor, gradientColor2.CGColor, gradientColor3.CGColor], [0, 0.43, 1])

        let rectangleRect = CGRectMake(frame.origin.x, frame.origin.y, frame.size.width, frame.size.height)
        let rectanglePath = UIBezierPath(rect: rectangleRect)
        CGContextSaveGState(context)
        rectanglePath.addClip()
        CGContextDrawLinearGradient(context, sVGID_1_4, CGPointMake(rectangleRect.minX, rectangleRect.midY),CGPointMake(rectangleRect.maxX, rectangleRect.midY), 0)
        CGContextRestoreGState(context)
    }

Answer 2

或者你可以使用我自己写的这个:) https://github.com/BilalReffas/SwiftyGradient

Answer 3

Swift 4 版本的来自@Loxx answer above 的第一个形状，它产生以下输出：

.

private func drawShape() {
    guard let context = UIGraphicsGetCurrentContext() else {
        print("No context, handle me")
        return
    }

    let gradientColor3 = UIColor(red: 1.000, green: 1.000, blue: 1.000, alpha: 1.000)
    let gradientColor4 = UIColor(red: 0.000, green: 1.000, blue: 0.000, alpha: 1.000)

    guard let sVGID_1_2 = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(), colors: [gradientColor3.cgColor, gradientColor4.cgColor] as CFArray, locations: [0, 1]) else {
        print("No gradient, handle me")
        context.restoreGState()
        return
    }

    context.saveGState()
    context.translateBy(x: 198.95, y: 199.4)
    context.rotate(by: -30 * CGFloat(Double.pi) / 180)

    let polygonPath = UIBezierPath()
    polygonPath.move(to: CGPoint(x: 0, y: -145.95))
    polygonPath.addLine(to: CGPoint(x: 126.4, y: -72.98))
    polygonPath.addLine(to: CGPoint(x: 126.4, y: 72.97))
    polygonPath.addLine(to: CGPoint(x: 0, y: 145.95))
    polygonPath.addLine(to: CGPoint(x: -126.4, y: 72.98))
    polygonPath.addLine(to: CGPoint(x: -126.4, y: -72.97))
    polygonPath.close()
    context.saveGState()
    polygonPath.addClip()
    context.drawLinearGradient(sVGID_1_2,
                               start: CGPoint(x: -126.4, y: -72.97),
                               end: CGPoint(x: 126.41, y: 72.99),
                               options: [.drawsBeforeStartLocation, .drawsAfterEndLocation])
    context.restoreGState()
}

我发布它是因为基本上每一行在转换为 Swift 4 时都发生了变化，并且需要一段时间来转换它以检查它是否有效。