wpf 鼠标操作画圆形

你可以使用WPF中的Canvas控件和鼠标事件来实现鼠标操作画圆形的功能。以下是一个简单的示例代码：

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Canvas x:Name="canvas" Background="White" MouseDown="Canvas_MouseDown" MouseMove="Canvas_MouseMove" MouseUp="Canvas_MouseUp"/>
    </Grid>
</Window>

private bool isDrawing = false;
private Point startPoint;
private Ellipse ellipse;

private void Canvas_MouseDown(object sender, MouseButtonEventArgs e)
{
    startPoint = e.GetPosition(canvas);
    ellipse = new Ellipse
    {
        Stroke = Brushes.Black,
        StrokeThickness = 1
    };
    Canvas.SetLeft(ellipse, startPoint.X);
    Canvas.SetTop(ellipse, startPoint.Y);
    canvas.Children.Add(ellipse);
    isDrawing = true;
}

private void Canvas_MouseMove(object sender, MouseEventArgs e)
{
    if (isDrawing)
    {
        double x = Math.Min(e.GetPosition(canvas).X, startPoint.X);
        double y = Math.Min(e.GetPosition(canvas).Y, startPoint.Y);
        double width = Math.Abs(e.GetPosition(canvas).X - startPoint.X);
        double height = Math.Abs(e.GetPosition(canvas).Y - startPoint.Y);
        ellipse.Width = width;
        ellipse.Height = height;
        Canvas.SetLeft(ellipse, x);
        Canvas.SetTop(ellipse, y);
    }
}

private void Canvas_MouseUp(object sender, MouseButtonEventArgs e)
{
    isDrawing = false;
}

在这个例子中，我们在Canvas上添加了MouseDown、MouseMove和MouseUp事件的处理程序。当鼠标按下时，我们记录起始点并创建一个新的Ellipse对象。在MouseMove事件中，我们根据鼠标的位置调整Ellipse的大小和位置。当鼠标松开时，绘制过程结束。