UIGraphicsBeginImageContext 阴影输出与 SwiftUI 视图阴影修饰符不同

问：

我想将一个图像拟合到另一个具有阴影效果的图像上。首先，我按如下方式构建 swiftUI 视图，然后尝试使用 UIGraphicsBeginImageContext 获得相同的输出。但不幸的是，这里发现了问题：输出图像中的阴影模糊与视图不同。我正在寻找合适的解决方案。

struct ContentView: View {
    @State private var imageRect : CGRect = .zero
    
    @State private var shadowBlur = 40.0
    @State private var shadowX = 100.0
    @State private var shadowY = 100.0
    
    var body: some View {
        VStack {
            GeometryReader(content: { geometry in
                ZStack {
                    Image("background")
                        .resizable()
                        .scaledToFit()
                        .overlay {
                            Image("foreground")
                                .resizable()
                                .scaledToFit()
                                .shadow(color: Color.red, radius: CGFloat(shadowBlur), x: shadowX, y: shadowY)
                        }
                        .clipped()
                        .background(GeometryGetter(rect: $imageRect))
                }
                .frame(width: geometry.size.width, height: geometry.size.height)
            })
            
            Button("Click") {
                let fgImage = UIImage(named: "foreground")!
                let bgImage = UIImage(named: "background")!
                
                let scale = bgImage.size.width / imageRect.width
                let fgFrame = fgImage.size.scaleSizeToFit(in: bgImage.size)
                let fggImage = fgImage.resize(targetSize: fgFrame)
                
                UIGraphicsBeginImageContext(bgImage.size)
                bgImage.draw(at: CGPoint.zero)
                let context = UIGraphicsGetCurrentContext()
                context?.setShadow(offset: CGSize(width: shadowX * scale, height: shadowY * scale), blur: shadowBlur * scale, color: UIColor.red.cgColor)
                let imageDrawPoint = CGPoint(x: bgImage.size.width/2.0 - fggImage.size.width / 2.0, y: bgImage.size.height/2.0 - fggImage.size.height / 2.0)
                fggImage.draw(at: imageDrawPoint)
                
                let outputImage = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()
                print("SUCCESS")
                
            }
        }
    }
}

extension UIImage {
    func resize(targetSize: CGSize) -> UIImage {
        let image = self.toCIImage()
        let scaleX = targetSize.width / image.extent.size.width
        let scaleY = targetSize.height / image.extent.size.height
        let scaleTransform = CGAffineTransform(scaleX: scaleX, y: scaleY)
        let scaledImage = image.transformed(by: scaleTransform)
        return scaledImage.toUIImage()
    }
}

extension CGSize {
    func scaleSizeToFit(in canvas: CGSize) -> CGSize {
        let widthScale = canvas.width / self.width
        let heightScale = canvas.height / self.height
        let scale = min(widthScale, heightScale)
        let scaledSize = CGSize(width: self.width * scale, height: self.height * scale)
        return scaledSize
    }
}

struct GeometryGetter: View {
    @Binding var rect: CGRect

    var body: some View {
        GeometryReader { (g) -> Path in
            print("width: \(g.size.width), height: \(g.size.height)")
            DispatchQueue.main.async {
                self.rect = g.frame(in: .global)
            }
            return Path()
        }
    }
}