Take capture a view by SwiftUI

convert.swift

//
//  ContentView.swift
//  TryGeometryReader
//
//  Created by satoutakeshi on 2019/12/07.
//  Copyright © 2019 satoutakeshi. Licensed under MIT.
//

import SwiftUI

struct ContentView: View {
    var body: some View {
        ScrollView {
            VStack {
                Text("GeometryReader Get Grobal Origin")
                GeometryRectangle(color: Color.pink)
                GeometryRectangle(color: Color.red)
                .offset(x: 10, y: 0)
                ZStack {
                    GeometryRectangle(color: Color.blue)
                        .offset(x: 30, y: 0)
                }
            }
        }
    }
}

struct GeometryRectangle: View {
    var color: Color
    var body: some View {
        GeometryReader { geometry in
            VStack {

                Button(action: {
                    let image = self.takeScreenshot(origin: geometry.frame(in: .global).origin, size: geometry.size)
                    print(image)
                }) {
                    RoundedRectangle(cornerRadius: 20)
                    .fill(self.color)
                    .overlay(
                        VStack {
                            Text("X: \(Int(geometry.frame(in: .global).origin.x)) Y: \(Int(geometry.frame(in: .global).origin.y)) width: \(Int(geometry.frame(in: .global).width)) height: \(Int(geometry.frame(in: .global).height))")
                                .foregroundColor(.white)
                            Text("size: \(geometry.size.debugDescription)")
                                .foregroundColor(.white)
                })}
            }

        }.frame(height: 100)
    }
}

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

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
    }
}

Thank you Satoさん.
But I still have a question.
Now I have a ScrollView embedded inside a GeometryReader, and the content size of the ScrollView has a height that is greater than the size of the GeometryProxy, how can I get the full scrollable content be converted to image instead of the visible contents only?

This used to work amazing for my app. Thank you very much for that. However since iOS14 I get an error at self.layer.render(in: context). AttributeGraph precondition failure: setting value during update: 22552.

The app freezes and xCode says the typical Thread 1: signal SIGABRT

Any help would be greatly appreciated.

@keatsp can you post code somewhere? works fine for me

I get a similar issue. I am trying to take a screenshot of a view that is not being displayed. This is probably the issue. I was attempting to take a "preview" of a view to display in a context menu. I am getting this error:

2021-04-11 22:20:44.770952-0400 _____[1967:259741] [error] precondition failure: setting value during update: 764440
AttributeGraph precondition failure: setting value during update: 764440.

and

Thread 1: signal SIGABRT

I have the same issue as @claytonsulby and @keatsp