iOS颜色渐变

方法1：
 //图片边缘模糊

        let colorLayer =CAGradientLayer()
        colorLayer.frame =circleImageIcon.frame
        colorLayer.position =circleImageIcon.center
        //设置渐变颜色及透明度
        colorLayer.colors = [UIColor(red:250 /255.0,
green:250 /255.0, blue:250 /255.0, alpha:0.1).CGColor,UIColor(red:250
/255.0, green:250 /255.0, blue:250 /255.0,
alpha:0.5).CGColor,UIColor(red:250 /255.0,
green:250 /255.0, blue:250 /255.0, alpha:1.0).CGColor]
        //颜色分割线
        colorLayer.locations = [0.5,0.75]
        //颜色起止点
        colorLayer.startPoint =CGPointMake(0.5,0)
        colorLayer.endPoint =CGPointMake(1,0)
        circleImageIcon.layer.insertSublayer(colorLayer, atIndex:0)
方法2

新建一个类继承于UIVIew，重写drawRect方法，
 //获取上下文
        let context =UIGraphicsGetCurrentContext()
//        let gradient: CGGradientRef
        let colorSpace =CGColorSpaceCreateDeviceRGB()
        //颜色渐变组件,一组四个数字分别对应rgb透明度
        let componets:[CGFloat] = [220.0,220.0, 220.0,0.1,220.0,220.0,220.0, 1]
        //定义渐变位置
        let locations:[CGFloat] = [0,1]
        let gradient =CGGradientCreateWithColorComponents(colorSpace, componets, locations,2)!
        //绘制线性渐变
        CGContextDrawLinearGradient(context, gradient,CGPointMake(0, rect.size.height),CGPointMake(rect.size.width,
rect.size.height),CGGradientDrawingOptions.DrawsAfterEndLocation)