swift - 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UIImage与它一起旋转（任何自定义角度）。我知道有经典的方式CGContextRotateCTM。

Answer 1

您可以设置 UIGraphicsImageRenderer 来创建图像并调用 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

建立在@reza23 的回答之上。你不需要调用 UIGraphicsGetCurrentContext，你可以使用渲染器的上下文。

extension UIImage
{
    public func rotate(angle:CGFloat)->UIImage
    {
        let radians = CGFloat(angle * .pi) / 180.0 as CGFloat
        
        var newSize = CGRect(origin: CGPoint.zero, size: self.size).applying(CGAffineTransform(rotationAngle: radians)).size
        
        // Trim off the extremely small float value to prevent core graphics from rounding it up
        newSize.width = floor(newSize.width)
        newSize.height = floor(newSize.height)
        let renderer = UIGraphicsImageRenderer(size:newSize)
        
        let image = renderer.image
        { rendederContext in
            
            let context = rendederContext.cgContext
            //rotate from center
            context.translateBy(x: newSize.width/2, y: newSize.height/2)
            context.rotate(by: radians)
            draw(in:  CGRect(origin: CGPoint(x: -self.size.width/2, y: -self.size.height/2), size: size))
        }
        
        return image
    }
}

Answer 3

浏览文档，也由于缺乏对这个问题的答复，我认为新的UIGraphicsImageRenderer. 这是我在一天结束时解决它的方法：

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 Size对应于绘制旋转图像而不改变其整体大小所需的矩形区域。然后在中心旋转和绘制图像。有关这方面的更多信息，请参阅这篇文章。