CGPointZero和CGContextDrawImage不可用。

Question

我无法将CGContextDrawImage转换为Swift 3，我尝试了context.draw但它不起作用。是否有人可以给我反馈？

错误截图

代码:

import UIKit

public struct Pixel {
public var value: UInt32

public var red: UInt8 {
    get {
        return UInt8(value & 0xFF)
    }
    set {
        value = UInt32(newValue) | (value & 0xFFFFFF00)
    }
}

public var green: UInt8 {
    get {
        return UInt8((value >> 8) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 8) | (value & 0xFFFF00FF)
    }
}

public var blue: UInt8 {
    get {
        return UInt8((value >> 16) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 16) | (value & 0xFF00FFFF)
    }
}

public var alpha: UInt8 {
    get {
        return UInt8((value >> 24) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 24) | (value & 0x00FFFFFF)
    }
}

public struct RGBAImage {
public var pixels: [Pixel]

public var width: Int
public var height: Int

public init?(image: UIImage) {
    guard let cgImage = image.cgImage else { return nil }

    // Redraw image for correct pixel format
    let colorSpace = CGColorSpaceCreateDeviceRGB()

    var bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue
    bitmapInfo |= CGImageAlphaInfo.premultipliedLast.rawValue & CGBitmapInfo.alphaInfoMask.rawValue

    width = Int(image.size.width)
    height = Int(image.size.height)
    let bytesPerRow = width * 4

    let imageData = UnsafeMutablePointer<Pixel>.allocate(capacity: width * height)

    guard let imageContext = CGContext(data: imageData, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) else { return nil }
    CGContextDrawImage(imageContext, CGRect(origin: CGPointZero, size: image.size), cgImage)

    let bufferPointer = UnsafeMutableBufferPointer<Pixel>(start: imageData, count: width * height)
    pixels = Array(bufferPointer)

    imageData.deinitialize()
    imageData.deallocate(capacity: width * height)
}

public func toUIImage() -> UIImage? {
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    var bitmapInfo: UInt32 = CGBitmapInfo.byteOrder32Big.rawValue
    bitmapInfo |= CGImageAlphaInfo.premultipliedLast.rawValue & CGBitmapInfo.alphaInfoMask.rawValue

    let bytesPerRow = width * 4

    let imageDataReference = UnsafeMutablePointer<Pixel>(mutating: pixels)
    defer {
        imageDataReference.deinitialize()
    }
    let imageContext = CGContext(data: imageDataReference, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo, releaseCallback: nil, releaseInfo: nil)

    guard let cgImage = imageContext!.makeImage() else {return nil}
    let image = UIImage(cgImage: cgImage)

    return image
}

- Alperen Veli Sezer

---

你可以在 Stack Overflow 上找到一些例子，比如 这个 或者 这个。而且我在你的代码中也没有找到 _tried context.draw_。 - OOPer

为了格式化您的代码，请不要添加块引用，而是选择代码，然后执行CMD+K。我曾经这样做过，但是由于后续编辑而失败了 - 请重新格式化。谢谢。 - Eric Aya

在Swift 3中，它是CGPoint.zero和context.draw(...)。 - Codo

CGSizeZero和CGSizeMake在Swift 2.0中可用，在Swift 3.0中您可以使用CGSize和CGRect。 - Himanshu Moradiya

@Alperen：你最好提供一个不起作用的context.draw示例，而不是CGContextDrawImage函数。 - alexburtnik

Answer 1

所有的CoreGraphics C函数都被重构，以更好地适应Swift风格：

Swift 2：

CGContextDrawImage(imageContext, CGRect(origin: CGPointZero, size: image.size), cgImage)

Swift 3：

imageContext.draw(cgImage, in: CGRect(origin: .zero, size: image.size))

附注：可以使用.zero代替CGPoint.zero，因为它的类型可以被隐式推断。

- alexburtnik