Render a SwiftUI view into an image with opacity - swiftui

Question

I need to render a SwiftUI view into an image with opacity, so that empty space of the view would be transparent when I layer the image above some background.
I use this code for conversion:
func convertViewToData<V>(view: V, size: CGSize) -> UIImage? where V: View {
guard let rootVC = UIApplication.shared.windows.first?.rootViewController else {
return nil
}
let imageVC = UIHostingController(rootView: view.edgesIgnoringSafeArea(.all))
imageVC.view.frame = CGRect(origin: .zero, size: size)
rootVC.view.insertSubview(imageVC.view, at: 0)
let uiImage = imageVC.view.asImage(size: size)
imageVC.view.removeFromSuperview()
return uiImage
}
extension UIView {
func asImage(size: CGSize) -> UIImage {
let format = UIGraphicsImageRendererFormat()
format.opaque = false
return UIGraphicsImageRenderer(bounds: bounds, format: format).image { context in
layer.render(in: context.cgContext)
}
}
}
extension View{
func convertToImage(size: CGSize) -> UIImage?{
convertViewToData(view: self, size: size)
}
}
And this code to test the resulting image:
struct ContentView: View {
var view: some View{
VStack {
Image(systemName: "globe")
.imageScale(.large)
.foregroundColor(.accentColor)
Text("Hello, world!")
}
}
var body: some View {
HStack{
view
Image(uiImage: view.convertToImage(size: .init(width: 200, height: 200))!)
}
.background(LinearGradient(stops: [.init(color: .green, location: 0), .init(color: .red, location: 1)], startPoint: .bottom, endPoint: .top))
}
}
This code produces two instances of the text: the one on the left is layered on the gradient background, and the one on the right is on the black background:
Clearly, the transparent parts are replaced by the black color in the image.
I figured out that the alpha information is discarded somewhere in the convertViewToData, but I was not able to find a way to preserve it.