The original code to resize UIImage

UIImage+Resize.swift

extension UIImage {
    
    func resizedImage(newSize:CGSize) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
        self.drawInRect(CGRectMake(0, 0, newSize.width, newSize.height))
        let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
    
    /// Resize image, keep the aspect ratio
    func resizedImageWithAspectFit(newSize:CGSize) -> UIImage {
        // Resize with aspect
        var resizeFactor = size.width / newSize.width
        if size.height > size.width {
            // But if height is bigger
            resizeFactor = size.height / newSize.height
        }
        let newSizeFixedAspect = CGSizeMake(size.width/resizeFactor, size.height/resizeFactor)
        let resized = resizedImage(newSizeFixedAspect)
        return resized
    }
    
}