把SwiftUI View 转为图片

方法1： 使用 drawHierarchy

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)
        }
    }
}

注意：这个方法需要swiftUI view 设置 .edgesIgnoringSafeArea(.all)

完整demo:

struct ContentView: View {
    var textView: some View {
        VStack{
            Text("ABCSF1")
            Text("ABCSF2")
            Text("ABCSF3")
            Text("Hello, SwiftUI")
                .padding()
                .background(.blue)
                .foregroundStyle(.white)
                .clipShape(Capsule())
        }
        .edgesIgnoringSafeArea(.all)
    }

    var body: some View {
        VStack {
            textView

            Button("Save to image") {
                let image = textView.snapshot()

                UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
            }
        }
        .edgesIgnoringSafeArea(.all)

    }
}

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)
        }
    }
}

方法2： 使用ImageRenderer，需要iOS16以上

struct RenderView: View {
    let text: String

    var body: some View {
        Text(text)
            .font(.largeTitle)
            .foregroundStyle(.white)
            .padding()
            .background(.blue)
            .clipShape(Capsule())
    }
}

struct ContentView: View {
    @State private var text = "Your text here"
    @State private var renderedImage = Image(systemName: "photo")
    @Environment(\.displayScale) var displayScale

    var body: some View {
        VStack {
            renderedImage

            ShareLink("Export", item: renderedImage, preview: SharePreview(Text("Shared image"), image: renderedImage))

            TextField("Enter some text", text: $text)
                .textFieldStyle(.roundedBorder)
                .padding()
        }
        .onChange(of: text) { _ in render() }
        .onAppear { render() }
    }

    @MainActor
    func render() {
        let renderer = ImageRenderer(content: RenderView(text: text))
        
        // make sure and use the correct display scale for this device
        renderer.scale = displayScale

        if let uiImage = renderer.uiImage {
            renderedImage = Image(uiImage: uiImage)
        }
    }
}

参考文章：

www.hackingwithswift.com/quick-start…

swdevnotes.com/swift/2022/…