[Swift] UIImageをリサイズする方法メモ

October 25, 2019

画像をリサイズしてから保存、送信するケースが多いのでそのとき用のメモ

リサイズ用のエクステンション

extension UIImage {
    func resized(withPercentage percentage: CGFloat) -> UIImage? {
        let canvas = CGSize(width: size.width * percentage, height: size.height * percentage)
        return UIGraphicsImageRenderer(size: canvas, format: imageRendererFormat).image {
            _ in draw(in: CGRect(origin: .zero, size: canvas))  
        }
    }
    func resized(toWidth width: CGFloat) -> UIImage? {
        let canvas = CGSize(width: width, height: CGFloat(ceil(width/size.width * size.height)))
        return UIGraphicsImageRenderer(size: canvas, format: imageRendererFormat).image {
            _ in draw(in: CGRect(origin: .zero, size: canvas))
        }
    }
}

使い方

let image = UIImage(data: try! Data(contentsOf: URL(string:"http://i.stack.imgur.com/Xs4RX.jpg")!))!

let thumb1 = image.resized(withPercentage: 0.1)
let thumb2 = image.resized(toWidth: 72.0)

Xcode9・Swift4以降で動く