Swift 3 和 CGContextDrawImage

Question

我想将此行翻译成 Swift 3 当前语法代码，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将CGContextDrawImage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

当我尝试这样做时:

 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）：

任何人都可以帮我解决这个新的 swift 3 语法代码吗？

Answer 1

你需要把它当作CGContext的实例方法来调用:

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

检查the latest reference of CGContext。

Answer 2

我找到了另一个非常好的解决方案来解决我目前正在使用的这个问题。在使用 UIImagePickerController 捕获图像后，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。它使用 UIImageOrientaiton 检查图像的 EXIF 属性并根据方向值进行转换和缩放图像，因此您将获得与相机视图方向相同的 return 图像。

这里我保留了 3000 的最大分辨率，这样在您使用 Retina 设备时图像质量不会受到特别破坏，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!
    }

Swift 3 和 CGContextDrawImage

Swift 3 and CGContextDrawImage

core-graphics

swift3