SwiftUI视图到AppKit中的NSImage

Question

SwiftUI 2.0 # Swift 5.4 \ Xcode 12.4 \x{e76f} macOS大Sur 11.4

在iOS中，有一种方法可以将SwiftUI视图呈现给在AppKit中不工作的UIImage，只有UIKit：

extension View {
    func snapshot() -> UIImage {
        let controller = UIHostingController(rootView: self)
        let view = controller.view

        let targetSize = controller.view.intrinsicContentSize
        view?.bounds = CGRect(origin: .zero, size: targetSize)
        view?.backgroundColor = .clear

        let renderer = UIGraphicsImageRenderer(size: targetSize)

        return renderer.image { _ in
            view?.drawHierarchy(in: controller.view.bounds, afterScreenUpdates: true)
        }
    }
}

在AppKit上有什么办法可以解决这个问题吗？UIGraphicsImageRenderer(size:)方法不适用于AppKit，也没有等效的方法。

Answer 1

如果我正确地理解了你的问题，你应该能够使用NSBitmapImageRef来完成这个任务！

下面是一个从NSImage视图生成SwiftUI的简单示例(注意:您的主机视图必须是可见的！)：

let view = MyView() // some SwiftUI view
let host = NSHostingView(rootView: view)

// Note: the host must be visible on screen, which I am guessing you already have it that way. If not, do that here.

let bitmapRep = host.bitmapImageRepForCachingDisplay(in: host.bounds)
host.cacheDisplay(in: host.bounds, to: bitmapRep!)

let image = NSImage(size: host.frame.size)
image.addRepresentation(bitmapRep!)

下面是NSHostingView的一个扩展，可以安全地生成快照：

extension NSHostingView {
    func snapshot() -> NSImage? {
        // Make sure the view is visible:
        guard self.window != nil else { return nil }

        // Get bitmap data:
        let bitmapRep = self.bitmapImageRepForCachingDisplay(in:
        self.bounds)
        self.cacheDisplay(in: self.bounds, to: bitmapRep!)

        // Create NSImage from NSBitmapImageRep:
        let image = NSImage(size: self.frame.size)
        image.addRepresentation(bitmapRep!)
        
        return image
    }
}

我希望这能帮到你。如果你有什么问题请告诉我！