[Swift]UIImage图片旋转

比如项目有“点赞”和“点踩”两个切图，有了图片旋转就可以只导入一个切图。

    let dzImg = UIImage(named: "icon_dz")!
    let dcImg = flipImage(dzImg)

    // UIImage图片旋转
    private func flipImage(_ image: UIImage) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(image.size, false, image.scale)
        let context = UIGraphicsGetCurrentContext()!
        context.translateBy(x: image.size.width / 2, y: image.size.height / 2)
        context.rotate(by: CGFloat.pi*2)
        context.translateBy(x: -image.size.width / 2, y: -image.size.height / 2)
        context.draw(image.cgImage!, in: CGRect(origin: .zero, size: image.size))
        let flippedImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return flippedImage
    }