Utility for UIImage

UIImageExtension.swift

public extension UIImage {
    /// 画像を指定したサイズでリサイズする
    /// @see https://qiita.com/ruwatana/items/473c1fb6fc889215fca3
    func resized(to size: CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, opaque, scale)
        draw(in: CGRect(origin: .zero, size: size))
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }

    /// 画像を指定したサイズで上部から切り抜く
    /// @see https://qiita.com/takabosoft/items/391b7593f0b9ef7d77a5
    func cropped(to size: CGSize) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, opaque, scale)
        draw(at: CGPoint(x: 0, y: 0))
        let result = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return result
    }

    private var opaque: Bool {
        if let cgImage = cgImage {
            switch cgImage.alphaInfo {
            case .noneSkipLast, .noneSkipFirst:
                return true
            default:
                break
            }
        }
        return false
    }
}