UIKit 프레임워크를 사용한 이미지 리사이징

UIImage+Extension.swift

extension UIImage {
    func resizeUI(size:CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, true, self.scale)
        self.drawInRect(CGRect(origin: CGPointZero, size: size))
        
        let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return resizedImage
    }
}