有时候我们需要从一个16进制的颜色代码(例如#fafcfe)获得一个颜色对象，可以使用如下方法:

func hexColorString(_ color:String,alpha:Float=1.0)->UIColor{

var colorString=color.trimmingCharacters(in:.whitespacesAndNewlines).lowercased()

if colorString.characters.count<6{

return UIColor.clear

}

if colorString.hasPrefix("0x"){

colorString=colorString.replacingOccurrences(of: "0x", with: "")

}

else if colorString.hasPrefix("#"){

colorString=colorString.replacingOccurrences(of: "#", with: "")

}

if colorString.characters.count != 6{

return UIColor.clear

}

let colorStr=NSString(string:colorString)

var range=NSRange(location: 0,length: 2)

let redString=colorStr.substring(with: range)

range.location = 2

let greenString=colorStr.substring(with: range)

range.location = 4

let blueString=colorStr.substring(with: range)

var red:UInt32=0

var green:UInt32=0

var blue:UInt32=0

var success=Scanner(string: redString).scanHexInt32(&red)

if !success{

return UIColor.clear

}

success=Scanner(string: greenString).scanHexInt32(&green)

if !success{

return UIColor.clear

}

success=Scanner(string: blueString).scanHexInt32(&blue)

if !success{

return UIColor.clear

}

return UIColor(red:CGFloat(red)/255,green:CGFloat(green)/255,blue:CGFloat(blue)/255,alpha:CGFloat(alpha))

}

如果希望从r,g,b三原色获得颜色对象则可以使用如下方法:

 func color(_ red:UInt8,green:UInt8,blue:UInt8,alpha:UInt8=0xff)->UIColor{

return UIColor(red:CGFloat(red)/255,green:CGFloat(green)/255,blue:CGFloat(blue)/255,alpha:CGFloat(alpha)/255)

}