UIBarButtonItem のアイコンをリサイズする

ResizingImageBarButtonItem.swift

import UIKit

extension UIImage {
    func scale(to newSize: CGSize) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
        draw(in: CGRect(x: 0.0, y: 0.0, width: newSize.width, height: newSize.height))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage ?? self
    }
}

@IBDesignable
class ResizingImageBarButtonItem: UIBarButtonItem {

    @IBInspectable
    var scaledRatio: CGFloat = 1.0 {
        didSet {
            guard let size = image?.size.applying(CGAffineTransform(scaleX: scaledRatio, y: scaledRatio)) else { return }
            image = image?.scale(to: size)
        }
    }

    @IBInspectable
    var scaledWidth: CGFloat = 0.0 {
        didSet {
            image = image?.scale(to: CGSize(width: scaledWidth, height: scaledHeight))
        }
    }

    @IBInspectable
    var scaledHeight: CGFloat = 0.0 {
        didSet {
            image = image?.scale(to: CGSize(width: scaledWidth, height: scaledHeight))
        }
    }

}