给UIImage添加extension（兼容Swift3 和Swift 4）
extension UIImage {
func scaled(withSize size: CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
defer { UIGraphicsEndImageContext() }
draw(in: CGRect(x: 0.0, y: 0.0, width: size.width, height: size.height))
return UIGraphicsGetImageFromCurrentImageContext()!
}
}
scaled()接收指定的尺寸缩放UIImage。
如果要按纵横比缩放到给定尺寸，可以添加以下extension：
extension UIImage {
func scaleToFitSize(size: CGSize) -> UIImage {
let aspect = self.size.width / self.size.height
if size.width / aspect <= size.height {
return scaledImage(withSize: CGSize(width: size.width, height: size.width / aspect))
} else {
return scaledImage(withSize: CGSize(width: size.height * aspect, height: size.height))
}
}
}
使用：
let image = UIImage(named: "apple")
let scaledImage = image.scaleToFitSize(size: CGSize(width: 50.0, height: 50.0))