CoreGraphics를 사용한 이미지 리사이징

UIImage+Extension.swift

extension UIImage {
    func resizeCG(size:CGSize) -> UIImage? {
        let bitsPerComponent = CGImageGetBitsPerComponent(self.CGImage)
        let bytesPerRow = CGImageGetBytesPerRow(self.CGImage)
        let colorSpace = CGImageGetColorSpace(self.CGImage)
        let bitmapInfo = CGImageGetBitmapInfo(self.CGImage)
        
        let context = CGBitmapContextCreate(nil, Int(size.width), Int(size.height), bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo.rawValue)
        CGContextSetInterpolationQuality(context, .High)
        
        CGContextDrawImage(context, CGRect(origin: CGPoint.zero, size: size), self.CGImage)
        
        return CGBitmapContextCreateImage(context).flatMap { UIImage(CGImage: $0) }        
    }
}