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 您可以尝试使用CombinedGeometry组合2个几何（每次）。 它具有GeometryCombineMode允许您指定一些逻辑组合。 在这种情况下，您需要的是GeometryCombineMode.Xor 。 将切除 Rect和Ellipse（cirlce）的交点。 以下是演示它的简单代码： 
 
DrawingVisual dv = new DrawingVisual();
using (var dc = dv.RenderOpen()) {                    
  var rect = new Rect(0, 0, 300, 200);        
  var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                                new RectangleGeometry(rect),
                               new EllipseGeometry(new Point(150, 100), 50, 50));
  dc.DrawGeometry(Brushes.Blue, null, cb);                    
}
 
 我希望你知道如何渲染DrawingVisual 。 您可以使用一些RenderTargetBitmap将其捕获到某种BitmapSource中，然后您可以通过多种方式显示此位图。 
 
 这是截图： 
 
 
 黑色区域表示颜色是透明的。 
 
 如果你想剪出一些复杂的图像（如绘制的文字或图像）。 您可以将CombinedGeometry转换为某种OpacityMask （ Brush类型）。 我们可以把它变成DrawingBrush ，这个画笔可以用作OpacityMask ，可以传递给DrawingContext.PushOpacityMask方法： 
 
DrawingVisual dv = new DrawingVisual();                
using (var dc = dv.RenderOpen()) {                    
  var rect = new Rect(0, 0, 300, 200);
  var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                                new RectangleGeometry(rect),
                               new EllipseGeometry(new Point(150, 100), 50, 50));
  var mask = new DrawingBrush(new GeometryDrawing(Brushes.Blue, null, cb));      
  dc.PushOpacityMask(mask);
  dc.DrawImage(someImage, rect);
  dc.DrawText(new FormattedText("Windows Presentation Foundation", 
                                 System.Globalization.CultureInfo.CurrentCulture, 
                                 System.Windows.FlowDirection.LeftToRight,
                                 new Typeface("Lucida Bright"), 30, Brushes.Red){ 
                                   MaxTextWidth = rect.Width, 
                                   MaxTextHeight = rect.Height, 
                                   TextAlignment = TextAlignment.Center
                                 }, new Point());
}
 
 
 请注意， rect应该具有整个图形的大小。 然后定位孔和其他绘制的东西将是你想要的精确。 
 
 最后， DrawingVisual还有一个名为Clip的有用属性，它是一个Geometry 。 因此，您可以准备一些CombinedGeometry并将其分配给DrawingVisual.Clip属性。 
 
 假设您已经拥有了DrawingVisual （包含一些绘制的内容，包括文本，图像......）。 以下代码将通过它打孔 ： 
 
//prepare the geometry, which can be considered as the puncher.
var rect = new Rect(0, 0, 300, 200);
var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                              new RectangleGeometry(rect),
                             new EllipseGeometry(new Point(150, 100), 50, 50));
//punch the DrawingVisual
yourDrawingVisual.Clip = cb;

You can try using CombinedGeometry to combine 2 geometries (each time). It has GeometryCombineMode allowing you to specify some logic combination. In this case what you need is GeometryCombineMode.Xor. The intersection of the Rect and the Ellipse (cirlce) will be cut out. Here is the simple code demonstrating it:
 
DrawingVisual dv = new DrawingVisual();
using (var dc = dv.RenderOpen()) {                    
  var rect = new Rect(0, 0, 300, 200);        
  var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                                new RectangleGeometry(rect),
                               new EllipseGeometry(new Point(150, 100), 50, 50));
  dc.DrawGeometry(Brushes.Blue, null, cb);                    
}
 
I hope you know how to render the DrawingVisual. You can use some RenderTargetBitmap to capture it into some kind of BitmapSource and then you have many ways to show this bitmap.
 
Here is the screenshot:
 
 
The Black region means the color is transparent.
 
In case you want to cut out some complex image (such as drawn text or image). You can turn the CombinedGeometry into some kind of OpacityMask (type of Brush). We can turn it into a DrawingBrush and this brush can be used as OpacityMask which can be passed into DrawingContext.PushOpacityMask method:
 
DrawingVisual dv = new DrawingVisual();                
using (var dc = dv.RenderOpen()) {                    
  var rect = new Rect(0, 0, 300, 200);
  var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                                new RectangleGeometry(rect),
                               new EllipseGeometry(new Point(150, 100), 50, 50));
  var mask = new DrawingBrush(new GeometryDrawing(Brushes.Blue, null, cb));      
  dc.PushOpacityMask(mask);
  dc.DrawImage(someImage, rect);
  dc.DrawText(new FormattedText("Windows Presentation Foundation", 
                                 System.Globalization.CultureInfo.CurrentCulture, 
                                 System.Windows.FlowDirection.LeftToRight,
                                 new Typeface("Lucida Bright"), 30, Brushes.Red){ 
                                   MaxTextWidth = rect.Width, 
                                   MaxTextHeight = rect.Height, 
                                   TextAlignment = TextAlignment.Center
                                 }, new Point());
}
 
 
Note that the rect should have the size of your whole drawing. Then positioning the hole and other drawn stuff will be exact as what you want.
 
Finally the DrawingVisual also has a useful property called Clip which is a Geometry. So you can prepare some CombinedGeometry and assign it to DrawingVisual.Clip property. 
 
Suppose you already have your DrawingVisual (with some drawn stuff including text, images, ...). The following code will punch a hole through it:
 
//prepare the geometry, which can be considered as the puncher.
var rect = new Rect(0, 0, 300, 200);
var cb = new CombinedGeometry(GeometryCombineMode.Xor, 
                              new RectangleGeometry(rect),
                             new EllipseGeometry(new Point(150, 100), 50, 50));
//punch the DrawingVisual
yourDrawingVisual.Clip = cb;