SwiftUIScreenShot.swift

import SwiftUI

struct StackGeometryReader: View {
    @Binding var takePic: Bool
    @State private var contentHeight: CGFloat = 0
    
    var body: some View {
        VStack {
            PrintableCells(color: Color.pink)
            PrintableCells(color: Color.red)
            PrintableCells(color: Color.green)
            PrintableCells(color: Color.pink)
            PrintableCells(color: Color.red)
            PrintableCells(color: Color.green)
            PrintableCells(color: Color.pink)
            PrintableCells(color: Color.red)
            PrintableCells(color: Color.green)
        }
        .padding()
        .background(
        ZStack {
            GeometryReader { proxy in
                Color.clear.onAppear() {
                    contentHeight = proxy.size.height
                }.onChange(of: takePic) { (newVal) in
                    if newVal {
                        let image = self.takeScreenshot(origin: proxy.frame(in: .global).origin, size: proxy.size)
                        print(image) //
                        takePic.toggle()
                    }
                }
            }
        })
    }
}

struct ContentView: View {
    @State private var takePic = false
    
    var body: some View {
        NavigationView {
            ScrollView {
                StackGeometryReader.init(takePic: $takePic)
            }.navigationTitle("Demo Screen Shot")
            .navigationBarItems(leading: Button(action: {
                takePic.toggle()
            }, label: {
              Text("Take pic")
            }))
        }
    }
    
}

struct PrintableCells: View {
    var color: Color
    var body: some View {
        GeometryReader { proxy in
            VStack {
                Button(action: {
                    let image = self.takeScreenshot(origin: proxy.frame(in: .global).origin, size: proxy.size)
                    print(image) //
                }) {
                    RoundedRectangle(cornerRadius: 20)
                    .fill(self.color)
                    .overlay(
                        VStack {
                            Text("size: \(proxy.size.debugDescription)")
                                .foregroundColor(.white)
                })}
            }
        }.frame(height: 100)
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

extension UIView {
    var screenShot: UIImage {
        let rect = self.bounds
        UIGraphicsBeginImageContextWithOptions(rect.size, false, 0.0)
        let context: CGContext = UIGraphicsGetCurrentContext()!
        self.layer.render(in: context)
        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.screenShot
    }
}