A method for converting a SwiftUI into a UIImage

SwiftUI-view-to-UIImage.swift

//
//  ContentView.swift
//  Grabber
//
//  SwiftUI-Lab
//
// For more information on the techniques used in this example, check
// The Power of the Hosting+Representable Combo (https://swiftui-lab.com/a-powerful-combo/)

import SwiftUI

struct ContentView: View {
    @State private var beginCapture = false
    @State private var image: UIImage? = nil
    
    var body: some View {
        
        VStack(spacing: 40) {
            HStack(spacing: 5) {
                ZStack {
                                        
                    RotatingSpheres(clockwise: false)
                        .frame(width: 300, height: 300)

                    RotatingSpheres(clockwise: true)
                        .onGrab(trigger: self.$beginCapture) { img in
                            DispatchQueue.main.async {
                                self.image = img
                            }
                        }
                        .frame(width: 300, height: 300)
                        .border(Color.black, width: 3)
                    
                    RotatingSpheres(clockwise: false)
                        .frame(width: 300, height: 300)
                    

                }

                // Captured Image
                Image(uiImage: self.image ?? UIImage())
                    .resizable()
                    .frame(width: 300, height: 300)
                    .border(Color.black, width: 3)

            }
            
            Button("Capture") { self.beginCapture = true }
        }
    }
}

struct RotatingSpheres: View {
    @State private var flag = false
    let clockwise: Bool
    
    var body: some View {
        VStack {
            HStack(spacing: 20) {
                Circle()
                    .fill(self.clockwise ? Color.orange : Color.red)
                    .frame(width: 80, height: 80)
                
                Circle()
                    .fill(self.clockwise ? Color.green : Color.blue)
                    .frame(width: 80, height: 80)

            }

            Circle()
                .fill(self.clockwise ? Color.yellow : Color.purple)
                .frame(width: 80, height: 80)

        }
        .onAppear {
            withAnimation(Animation.linear(duration: 5.0).repeatForever(autoreverses: false)) {
                self.flag = true
            }
        }
        .rotationEffect(self.flag ? (self.clockwise ? Angle.degrees(360) : Angle.degrees(-360)) : Angle.degrees(0))
    }
}

extension View {
    func onGrab(rect: CGRect? = nil, trigger: Binding<Bool>, onCapture: @escaping (UIImage) -> Void) -> some View {
        return CaptureWrapper(rect: rect, trigger: trigger, onCapture: onCapture) { self }
    }
}

struct CaptureWrapper<Content>: View where Content : View {
    let rect: CGRect?
    let trigger: Binding<Bool>
    let onCapture: (UIImage) -> Void
    let content: () -> Content

    init(rect: CGRect? = nil, trigger: Binding<Bool>, onCapture: @escaping (UIImage) -> Void, @ViewBuilder content: @escaping () -> Content) {
        self.rect = rect
        self.trigger = trigger
        self.onCapture = onCapture
        self.content = content
    }

    var body: some View {
        CaptureRepresentable(rect: rect, trigger: self.trigger, onCapture: self.onCapture, content: self.content())
    }
}

struct CaptureRepresentable<Content>: UIViewControllerRepresentable where Content: View {
    typealias UIViewControllerType = CaptureNSHostingController<Content>
    
    @Binding var trigger: Bool
    let rect: CGRect?
    let content: Content
    let onCapture: (UIImage) -> Void
    
    init(rect: CGRect?, trigger: Binding<Bool>, onCapture: @escaping (UIImage) -> Void, content: Content) {
        self.rect = rect
        self._trigger = trigger
        self.onCapture = onCapture
        self.content = content
    }
    
    func makeUIViewController(context: UIViewControllerRepresentableContext<CaptureRepresentable<Content>>) -> CaptureNSHostingController<Content> {
        return CaptureNSHostingController(rootView: self.content)
    }
    
    func updateUIViewController(_ uiViewController: CaptureNSHostingController<Content>, context: UIViewControllerRepresentableContext<CaptureRepresentable<Content>>) {
        if self.trigger {
            self.onCapture(uiViewController.getAsImage(rect: rect))
            
            DispatchQueue.main.async {
                self.trigger = false
            }
        }
        
    }
}

class CaptureNSHostingController<Content>: UIHostingController<Content> where Content : View {
    override func preferredContentSizeDidChange(forChildContentContainer container: UIContentContainer) {
    }
    
    func getAsImage(rect: CGRect? = nil) -> UIImage {
        if let rect = rect {
            return self.view.asImage(rect: rect)
        } else {
            return self.view.asImage(rect: self.view.bounds)
        }
    }
}

extension UIView {
    func asImage(rect: CGRect) -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: rect)
        return renderer.image { rendererContext in
            layer.render(in: rendererContext.cgContext)
        }
    }
}