一、实现的效果

代码实现

参考 // stackoverflow.com/questions/6…

public class OutlinedLabel: UILabel {
    
    public var outlineColor = UIColor.clear
    public var outlineWidth: CGFloat = 0
    
    override public func drawText(in rect: CGRect) {
        let shadowOffset = self.shadowOffset
        let textColor = self.textColor
        
        let c = UIGraphicsGetCurrentContext()
        c?.setLineWidth(outlineWidth)
        c?.setLineJoin(.round)
        c?.setTextDrawingMode(.stroke)
        if let gradientColor = drawGradientColor(in: rect, colors: [UIColor.blue.cgColor, UIColor.red.cgColor]) {
            self.textColor = gradientColor
        }
//        self.textColor = outlineColor;
        super.drawText(in: rect)
        
        c?.setTextDrawingMode(.fill)
        self.textColor = textColor
        self.shadowOffset = CGSize(width: 0, height: 0)
        super.drawText(in: rect)
        
        self.shadowOffset = shadowOffset
    }
    
    
    private func drawGradientColor(in rect: CGRect, colors: [CGColor]) -> UIColor? {
        let currentContext = UIGraphicsGetCurrentContext()
        currentContext?.saveGState()
        defer { currentContext?.restoreGState() }
        
        let size = rect.size
        UIGraphicsBeginImageContextWithOptions(size, false, 0)
        guard let gradient = CGGradient(colorsSpace: CGColorSpaceCreateDeviceRGB(),
                                        colors: colors as CFArray,
                                        locations: nil) else { return nil }
        
        let context = UIGraphicsGetCurrentContext()
        context?.drawLinearGradient(gradient,
                                    start: CGPoint.zero,
                                    end: CGPoint(x: size.width, y: 0),
                                    options: [])
        let gradientImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        guard let image = gradientImage else { return nil }
        return UIColor(patternImage: image)
    }
}

其他效果参考：

github.com/dungntm58/T…