pointers - 在 swift 中将 CFContextRef 转换为可变的 void 指针？

Question

我正在尝试将此 objc 代码转换为 swift:

CGContextRef contextRef = CGBitmapContextCreate(NULL,
                                                proposedRect.size.width,
                                                proposedRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                0,
                                                colorSpaceRef,
                                                (CGBitmapInfo)kCGImageAlphaPremultipliedFirst);
NSGraphicsContext *context = [NSGraphicsContext graphicsContextWithGraphicsPort:contextRef flipped:NO];

到目前为止，我得到了这个:

var bitmapContext: CGContext = CGBitmapContextCreate(data, UInt(proposedRect.width), UInt(proposedRect.height), CGImageGetBitsPerComponent(image), 0, colorSpace, CGBitmapInfo(CGImageAlphaInfo.PremultipliedFirst.toRaw()))
let context = NSGraphicsContext(graphicsPort: bitmapContext, flipped: false)

问题是 CGBitmapContextCreate 返回 CGContext 类型并且 NSGraphicsContext 初始化程序接受 graphicsPort 作为 CMutableVoidPointer 类型。那么如何将 CGContext 转换为 CMutableVoidPointer 呢？

在这里找到了相关的反向类型转换，但对我帮助不大 How to convert COpaquePointer in swift to some type (CGContext? in particular)

Answer 1

我最终使用 reinterpretCast 函数返回 bitmapContext 地址的中间 Int 变量。

var bitmapContext: CGContext = CGBitmapContextCreate(...)

let bitmapContextAddress: Int = reinterpretCast(bitmapContext)
let bitmapContextPointer: CMutableVoidPointer = COpaquePointer(UnsafePointer<CGContext>(bitmapContextAddress))
let context = NSGraphicsContext(graphicsPort: bitmapContextPointer, flipped: false)