ios - 如何从CGColorSpace获取Unmanaged <CGColorSpace>？

我正在Swift中编写一个函数，该函数从vImage_CGImageFormat创建CGImage，如下所示:

vImage_CGImageFormat(
    bitsPerComponent: UInt32(CGImageGetBitsPerComponent(image)),
    bitsPerPixel: UInt32(CGImageGetBitsPerPixel(image)),
    colorSpace: CGImageGetColorSpace(image),
    bitmapInfo: CGImageGetBitmapInfo(image),
    version: UInt32(0),
    decode: CGImageGetDecode(image),
    renderingIntent: CGImageGetRenderingIntent(image))

但是，这不会编译。这是因为CGImageGetColorSpace(image)返回CGColorSpace!，并且上述构造方法仅将Unmanaged<CGColorSpace>用作colorSpace参数。

还有另一种方法吗？也许将CGColorSpace转换为Unmanaged<CGColorSpace>？

最佳答案

这应该工作:

vImage_CGImageFormat(
    // ...
    colorSpace: Unmanaged.passUnretained(CGImageGetColorSpace(image)),
    //...
)

从struct Unmanaged<T> API文档中:

/// Create an unmanaged reference without performing an unbalanced
/// retain.
///
/// This is useful when passing a reference to an API which Swift
/// does not know the ownership rules for, but you know that the
/// API expects you to pass the object at +0.
///
/// ::
///
///   CFArraySetValueAtIndex(.passUnretained(array), i,
///                          .passUnretained(object))
static func passUnretained(value: T) -> Unmanaged<T>

Swift 3的更新:

vImage_CGImageFormat(
    // ...
    colorSpace: Unmanaged.passUnretained(image.colorSpace!),
    //...
)

关于ios - 如何从CGColorSpace获取Unmanaged <CGColorSpace>？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28361530/