使用UIGraphicsImageRenderer旋转图像？

Question

UIGraphicsImageRenderer是在iOS 10中新引入的。我想知道是否有可能用它旋转UIImage（任何自定义角度）。我知道有classic way与CGContextRotateCTM。

Answer 1

您可以设置UIGraphicsImageRenderer来创建一个图像，并通过该调用UIGraphicsGetCurrentContext（）并旋转上下文

    let renderer = UIGraphicsImageRenderer(size:sizeOfImage )
    let image = renderer.image(actions: { _ in
        let context = UIGraphicsGetCurrentContext()

        context?.translateBy(x: orgin.x, y: orgin.y)
        context?.rotate(by: angle)
        context?.draw(image.cgImage!, in: CGRect(origin: CGPoint(x: -orgin.x,y: -orgin.y), size: size))
    }
return image

Answer 2

通过文档，也由于缺乏对这个问题的回复，我认为新的UIGraphicsImageRenderer是不可能的。以下是我在一天结束时解决的问题：

func changeImageRotation(forImage image:UIImage, rotation alpha:CGFloat) -> UIImage{

    var newSize:CGSize{
        let a = image.size.width
        let b = image.size.height

        let width = abs(cos(alpha)) * a + abs(sin(alpha)) * b
        let height = abs(cos(alpha)) * b + abs(sin(alpha)) * a

        return CGSize(width: width, height: height)
    }

    let size = newSize
    let orgin = CGPoint(x: size.width/2, y: size.height/2)

    UIGraphicsBeginImageContext(size)
    let context = UIGraphicsGetCurrentContext()

    context?.translateBy(x: orgin.x, y: orgin.y)
    context?.rotate(by: alpha)
    context?.draw(image.cgImage!, in: CGRect(origin: CGPoint(x: -orgin.x,y: -orgin.y), size: size))

    let newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage!
}

New Sizecor响应绘制旋转图像所需的矩形区域，而不改变其整体大小。然后旋转图像并在中心绘制。有关更多信息，请参阅此post。