DrawingVisual.Drawing非常慢

Question

我想在一个现有的应用程序中迭代一些绘图（重新架构是一个没有吸引力的选项）。图纸存储为DrawingVisual对象：

foreach (DrawingVisual visual in TheDrawings)
{
    DrawingGroup group = visual.Drawing; // this is incredibly slow

    ...
}

我遇到的问题是DrawingVisual.Drawing属性getter非常慢。只需迭代一万个左右的视觉效果（没有做任何 它们，只是迭代）花费将近一秒钟，所有时间花在DrawingVisual.Drawing上。

深入研究WPF源代码，DrawingVisual.Drawing委托给ContainerVisual.GetDrawing，该代码解析为实用程序类DrawingServices中的这一昂贵调用：

internal static DrawingGroup DrawingGroupFromRenderData(RenderData renderData)
{
  DrawingGroup drawingGroup = new DrawingGroup();
  DrawingContext drawingContext = drawingGroup.Open();
  DrawingDrawingContext drawingDrawingContext = drawingContext as DrawingDrawingContext;
  if (drawingDrawingContext != null)
    drawingDrawingContext.CanBeInheritanceContext = false;
  DrawingContextDrawingContextWalker drawingContextWalker = new DrawingContextDrawingContextWalker(drawingContext);
  renderData.BaseValueDrawingContextWalk((DrawingContextWalker) drawingContextWalker);
  drawingContext.Close();
  return drawingGroup;
}

有没有人知道更好（即更快）的方式来迭代DrawingVisual的子项？