UIImage missed resize method via Swift extensions

UIImageExtensions.swift

extension UIImage {

    convenience init?(color: UIColor, size: CGSize = CGSizeMake(1, 1)) {
        let rect = CGRectMake(0, 0, size.width, size.height)
        UIGraphicsBeginImageContextWithOptions(rect.size, false, 0)
        let context = UIGraphicsGetCurrentContext()
        CGContextSetFillColorWithColor(context, color.CGColor)
        CGContextFillRect(context, rect)
        self.init(CGImage: UIGraphicsGetImageFromCurrentImageContext().CGImage!)
        UIGraphicsEndImageContext()
    }
    
    public func resize(width: CGFloat) -> UIImage {
        
        let scale = width / self.size.width
        let height = self.size.height * scale
        UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), false, UIScreen.mainScreen().scale)
        self.drawInRect(CGRectMake(0, 0, width, height))
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image
    }
    
}