ContextProblem.swift

import UIKit
import SwiftUI
import PlaygroundSupport
extension UIView {
    var renderedImage: UIImage {
        // rect of capure
        let rect = self.bounds
        // create the context of bitmap
        UIGraphicsBeginImageContextWithOptions(rect.size, false, 0.0)
        let context: CGContext = UIGraphicsGetCurrentContext()!
        self.layer.render(in: context)
        // get a image from current context bitmap
        let capturedImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return capturedImage
    }
}

extension View {
    func takeScreenshot(origin: CGPoint, size: CGSize) -> UIImage {
        let window = UIWindow(frame: CGRect(origin: origin, size: size))
        let hosting = UIHostingController(rootView: self)
        hosting.view.frame = window.frame
        window.addSubview(hosting.view)
        window.makeKeyAndVisible()
        return hosting.view.renderedImage
    }
}

class ImageStore: ObservableObject ,Identifiable{
    let id = UUID()
    var image: UIImage
    init(image: UIImage){
        self.image = image
    }
}

struct ContentView: View{
    @State var imageStore: ImageStore?
    var body: some View{
        NavigationView{
            GeometryReader{ geo in
                ZStack{
                    LinearGradient(gradient: Gradient(colors: [Color.blue,Color.white]), startPoint: .top, endPoint: .bottom)
                    Button(action: {
                        self.genImage(geo: geo)
                    }, label: {
                        Text("Create Image")
                            .foregroundColor(.white)
                    })
                }
            }
        }
        .sheet(item: $imageStore) { store in
            Image(uiImage: store.image)
        }
    }
    
    func genImage(geo: GeometryProxy){
        let image = self.takeScreenshot(origin: geo.frame(in: .global).origin, size: geo.size)
        self.imageStore = ImageStore(image: image)
    }
}


PlaygroundPage.current.setLiveView(ContentView())