从WPF应用程序窗口获取位图？

using System.Windows;
using System.Windows.Media;
using System.Windows.Media.Imaging;

public static BitmapSource GetWindowBitmap(Window window)
{
    int width = (int)window.ActualWidth;
    int height = (int)window.ActualHeight;

    RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap(width, height, 96, 96, PixelFormats.Pbgra32);
    renderTargetBitmap.Render(window);

    return renderTargetBitmap;
}

public static void SaveBitmapToFile(BitmapSource bitmap, string filePath)
{
    PngBitmapEncoder encoder = new PngBitmapEncoder();
    encoder.Frames.Add(BitmapFrame.Create(bitmap));

    using (FileStream fileStream = new FileStream(filePath, FileMode.Create))
    {
        encoder.Save(fileStream);
    }
}