UIBezierPath下绘制渐变

Question

我画了一条曲线。我想从视图一直到线条设置渐变（这样渐变会随着线条弯曲。）

编辑：这是下面代码生成的照片：

我知道如何画线，我知道如何添加规则的渐变，但只是不会将两者结合起来。这是我的代码：

override func drawRect(rect: CGRect) {

    // draw the curved line, this code works just fine.
    let path1 = UIBezierPath()
    path1.lineWidth = 1.1
    UIColor.greenColor().setStroke()
    path1.moveToPoint(CGPoint(x: 0, y: bounds.height/2))
    path1.addQuadCurveToPoint(CGPoint(x: bounds.width, y: bounds.height/2), controlPoint: CGPoint(x: bounds.width/2, y: (bounds.height * 0.75)))
    path1.stroke()

    // my attempt to draw the gradient:

    let gradient = CAGradientLayer()
    gradient.startPoint = CGPoint(x: 1, y: 1)
    gradient.endPoint = CGPoint(x: 0, y: 0)
    let colors = [UIColor.whiteColor().CGColor, UIColor(red: 0, green: 1, blue: 1, alpha: 0.4).CGColor]
    gradient.colors = colors

    // the following line is where I need help
    gradient.frame = CGRectMake(0, 475, bounds.width, path1.bounds.height)

    layer.addSublayer(gradient)


}

我可以将gradient.frame设置为什么，以便它的上限是之前绘制的路径？请在 Swift 中回答（我已经看到很多关于这个主题的其他问题，但它们都在 objective C 中）

谢谢

Answer 1

我找到了答案。

下面的代码给了我这个： .

代码如下：

   override func drawRect(rect: CGRect) {

    //draw the line of UIBezierPath 
    let path1 = UIBezierPath()
    path1.lineWidth = 1.1
    UIColor(white: 1, alpha: 1).setStroke()
    path1.moveToPoint(CGPoint(x: 0, y: bounds.height/2))
    path1.addQuadCurveToPoint(CGPoint(x: bounds.width, y: bounds.height/2), controlPoint: CGPoint(x: bounds.width/2, y: (bounds.height * 0.65)))

    path1.stroke()

  // add clipping path. this draws an imaginary line (to create bounds) from the 
   //ends of the UIBezierPath line down to the bottom of the screen
    let clippingPath = path1.copy() as! UIBezierPath
    clippingPath.addLineToPoint(CGPoint(x: self.bounds.width, y: self.bounds.height))
    clippingPath.addLineToPoint(CGPoint(x: 0, y: bounds.height))
    clippingPath.closePath()

    clippingPath.addClip()

    // create and add the gradient
    let colors = [UIColor(red: 0, green: 1, blue: 1, alpha: 0.45).CGColor, UIColor.whiteColor().CGColor]


    let colorSpace = CGColorSpaceCreateDeviceRGB()


    let colorLocations:[CGFloat] = [0.0, 1.0]


    let gradient = CGGradientCreateWithColors(colorSpace,
        colors,
        colorLocations)

    let context = UIGraphicsGetCurrentContext()
    let startPoint = CGPoint(x: 1, y: 1)
    let endPoint = CGPoint(x: 1, y: bounds.maxY)

    // and lastly, draw the gradient.
    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, CGGradientDrawingOptions.DrawsAfterEndLocation)



}

UIBezierPath下绘制渐变

Draw gradient under UIBezierPath

core-graphics

ios

uibezierpath

swift