Swift 3和CGContextDrawImage

Question

我想将这一行代码翻译成Swift 3的当前语法，但似乎存在一些问题：

CGContextDrawImage(context, CGRect(x:0.0,y: 0.0,width: image!.size.width,height: image!.size.height), image!.cgImage)

根据CoreGraphics.apinotes文件，CGContextDrawImage已经更改为CGContext.draw方法：

CoreGraphics.apinotes中指出CGContextDrawImage被转换为CGContext.draw。

Name: CGContextDrawImage
  # replaced by draw(_ image: CGImage, in rect: CGRect, byTiling: Bool = false)
  SwiftName: CGContext.__draw(self:in:image:)
  SwiftPrivate: true

当我尝试做：

 CGContext.draw(context as! CGImage, in: CGRect(x:0.0, y:0.0, width: image!.size.width, height: image!.size.height), byTiling: false) 

似乎有一些简单的语法错误干扰了编译器，但我看不到（实际上我收到了一个典型的模棱两可的错误）：

有人可以帮我解决这个新的 Swift 3 语法代码吗？

- Alessandro Ornano

Answer 1

你需要像调用CGContext的实例方法一样调用它：

context.draw(image!.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: image!.size.width,height: image!.size.height))

请查看CGContext的最新参考文档。

- OOPer

---

谢谢，它完美地工作了。示例的'self'初始属性使我分心了 :) - Alessandro Ornano

Answer 2

我已经找到了另一个非常好的解决方案，目前我正在使用它。在使用UIImagePickerController拍照后，您只需要将图像作为参数传递给此方法。它适用于所有版本的iOS，以及相机的纵向和横向方向。它使用UIImageOrientaiton检查图像的EXIF属性，并根据方向值转换和缩放图像，因此您将获得与相机视图方向相同的相同返回图像。

这里我将最大分辨率设置为3000，以便在使用视网膜设备时不会破坏图像质量，但您可以根据需要更改其分辨率。

func scaleAndRotateImage(image: UIImage, MaxResolution iIntMaxResolution: Int) -> UIImage {
        let kMaxResolution = iIntMaxResolution
        let imgRef = image.cgImage!
        let width: CGFloat = CGFloat(imgRef.width)
        let height: CGFloat = CGFloat(imgRef.height)
        var transform = CGAffineTransform.identity
        var bounds = CGRect.init(x: 0, y: 0, width: width, height: height)

        if Int(width) > kMaxResolution || Int(height) > kMaxResolution {
            let ratio: CGFloat = width / height
            if ratio > 1 {
                bounds.size.width = CGFloat(kMaxResolution)
                bounds.size.height = bounds.size.width / ratio
            }
            else {
                bounds.size.height = CGFloat(kMaxResolution)
                bounds.size.width = bounds.size.height * ratio
            }
        }
        let scaleRatio: CGFloat = bounds.size.width / width
        let imageSize = CGSize.init(width: CGFloat(imgRef.width), height: CGFloat(imgRef.height))

        var boundHeight: CGFloat
        let orient = image.imageOrientation
        // The output below is limited by 1 KB.
        // Please Sign Up (Free!) to remove this limitation.

        switch orient {
        case .up:
            //EXIF = 1
            transform = CGAffineTransform.identity
        case .upMirrored:
            //EXIF = 2
            transform = CGAffineTransform.init(translationX: imageSize.width, y: 0.0)
            transform = transform.scaledBy(x: -1.0, y: 1.0)

        case .down:
            //EXIF = 3
            transform = CGAffineTransform.init(translationX: imageSize.width, y: imageSize.height)
            transform = transform.rotated(by: CGFloat(Double.pi / 2))

        case .downMirrored:
            //EXIF = 4
            transform = CGAffineTransform.init(translationX: 0.0, y: imageSize.height)
            transform = transform.scaledBy(x: 1.0, y: -1.0)
        case .leftMirrored:
            //EXIF = 5
            boundHeight = bounds.size.height
            bounds.size.height = bounds.size.width
            bounds.size.width = boundHeight
            transform = CGAffineTransform.init(translationX: imageSize.height, y: imageSize.width)

            transform = transform.scaledBy(x: -1.0, y: 1.0)
            transform = transform.rotated(by: CGFloat(Double.pi / 2) / 2.0)
            break

        default: print("Error in processing image")
        }

        UIGraphicsBeginImageContext(bounds.size)
        let context = UIGraphicsGetCurrentContext()
        if orient == .right || orient == .left {
            context?.scaleBy(x: -scaleRatio, y: scaleRatio)
            context?.translateBy(x: -height, y: 0)
        }
        else {
            context?.scaleBy(x: scaleRatio, y: -scaleRatio)
            context?.translateBy(x: 0, y: -height)
        }
        context?.concatenate(transform)
        context?.draw(imgRef, in: CGRect.init(x: 0, y: 0, width: width, height: height))
        let imageCopy = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return imageCopy!
    }

- sajgan2015