【Swift】UIImageをリサイズする

UIImageExtension.swift

extension UIImageExtension {

	func resize(size: CGSize) -> UIImage {
		let widthRatio = size.width / self.size.width
		let heightRatio = size.height / self.size.height
		let ratio = (widthRatio < heightRatio) ? widthRatio : heightRatio
		let resizedSize = CGSize(width: (self.size.width * ratio), height: (self.size.height * ratio))
		UIGraphicsBeginImageContextWithOptions(resizedSize, false, 2)
		drawInRect(CGRect(x: 0, y: 0, width: resizedSize.width, height: resizedSize.height))
		let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
		UIGraphicsEndImageContext()
		return resizedImage
	}
	
	// 比率だけ指定する場合
	func resize(#ratio: CGFloat) -> UIImage {
		let resizedSize = CGSize(width: Int(self.size.width * ratio), height: Int(self.size.height * ratio))
		UIGraphicsBeginImageContextWithOptions(resizedSize, false, 2)
		drawInRect(CGRect(x: 0, y: 0, width: resizedSize.width, height: resizedSize.height))
		let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
		UIGraphicsEndImageContext()
		return resizedImage
	}
}

Aspect比を保ってリサイズするようにしました。