wpf 两点和半径之间的弧段

Arc Segment between two points and a radius

提问by Eggi

I am trying to paint an arc segment using WPF, but I somehow cannot figure out how to do this using the ArcSegment-Element.

我正在尝试使用 WPF 绘制弧段，但不知何故我无法弄清楚如何使用 ArcSegment-Element 执行此操作。

I have two points of the arc given (P1 and P2) and I also have the center of the circle and the radius.

我有给定的弧的两个点（P1 和 P2），我还有圆心和半径。

采纳答案by Clemens

Create a PathFigure with P1 as StartPointand an ArcSegment with P2 as Pointand a quadratic Sizethat contains the radius.

创建一个 P1 为的 PathFigureStartPoint和一个 P2 为的 ArcSegmentPoint以及一个Size包含半径的二次方。

Example: P1 = (150,100), P2 = (50,50), Radius = 100, i.e. Size=(100,100):

例子：P1 = (150,100), P2 = (50,50), Radius = 100, 即Size=(100,100):

<Path Stroke="Black">
    <Path.Data>
        <PathGeometry>
            <PathFigure StartPoint="150,100">
                <ArcSegment Size="100,100" Point="50,50"/>
            </PathFigure>
        </PathGeometry>
    </Path.Data>
</Path>

or shorter:

或更短：

<Path Stroke="Black" Data="M150,100 A100,100 0 0 0 50,50"/>

回答by johnml1135

I know this is a little old, but here goes a code version for a center and two angles - can be adapted to start and end points easily:

我知道这有点旧，但这里有一个中心和两个角度的代码版本 - 可以轻松适应起点和终点：

Outline:

大纲：

• Make a path and set the "top left" to 0,0 (You can still have center be negative if you want - this is just for path reference)
• Set up the boiler plate PathGeo and PathFigure (these are building blocks of the multi-segment path in Word etc.)
• Do angle checking
• If it is > 180 deg (pi radians), call it a "large angle"
• Find begining and end points and set them
• Based upon the math, it is a clockwise rotation (remember that positive Y is down, positive X is right)

• Set to canvas

  public void DrawArc(ref Path arc_path, Vector center, double radius, double start_angle, double end_angle, Canvas canvas)
  {
      arc_path = new Path();
      arc_path.Stroke = Brushes.Black;
      arc_path.StrokeThickness = 2;
      Canvas.SetLeft(arc_path, 0);
      Canvas.SetTop(arc_path, 0);
  
      start_angle = ((start_angle % (Math.PI * 2)) + Math.PI * 2) % (Math.PI * 2);
      end_angle = ((end_angle % (Math.PI * 2)) + Math.PI * 2) % (Math.PI * 2);
      if(end_angle < start_angle){
          double temp_angle = end_angle;
          end_angle = start_angle;
          start_angle = temp_angle;
      }
      double angle_diff = end_angle - start_angle;
      PathGeometry pathGeometry = new PathGeometry();
      PathFigure pathFigure = new PathFigure();
      ArcSegment arcSegment = new ArcSegment();
      arcSegment.IsLargeArc = angle_diff >= Math.PI;
      //Set start of arc
      pathFigure.StartPoint = new Point(center.X + radius * Math.Cos(start_angle), center.Y + radius * Math.Sin(start_angle));
      //set end point of arc.
      arcSegment.Point = new Point(center.X + radius * Math.Cos(end_angle), center.Y + radius * Math.Sin(end_angle));
      arcSegment.Size = new Size(radius, radius);
      arcSegment.SweepDirection = SweepDirection.Clockwise;
  
      pathFigure.Segments.Add(arcSegment);
      pathGeometry.Figures.Add(pathFigure);
      arc_path.Data = pathGeometry;
      canvas.Children.Add(arc_path);
  }
  

• 制作一条路径并将“左上角”设置为 0,0（如果需要，您仍然可以将中心设为负数 - 这仅用于路径参考）
• 设置样板 PathGeo 和 PathFigure（这些是 Word 等中多段路径的构建块）
• 做角度检查
• 如果大于 180 度（pi 弧度），则称其为“大角度”
• 找到起点和终点并设置它们
• 根据数学计算，它是顺时针旋转（记住正 Y 是向下，正 X 是右）

• 设置为画布

  public void DrawArc(ref Path arc_path, Vector center, double radius, double start_angle, double end_angle, Canvas canvas)
  {
      arc_path = new Path();
      arc_path.Stroke = Brushes.Black;
      arc_path.StrokeThickness = 2;
      Canvas.SetLeft(arc_path, 0);
      Canvas.SetTop(arc_path, 0);
  
      start_angle = ((start_angle % (Math.PI * 2)) + Math.PI * 2) % (Math.PI * 2);
      end_angle = ((end_angle % (Math.PI * 2)) + Math.PI * 2) % (Math.PI * 2);
      if(end_angle < start_angle){
          double temp_angle = end_angle;
          end_angle = start_angle;
          start_angle = temp_angle;
      }
      double angle_diff = end_angle - start_angle;
      PathGeometry pathGeometry = new PathGeometry();
      PathFigure pathFigure = new PathFigure();
      ArcSegment arcSegment = new ArcSegment();
      arcSegment.IsLargeArc = angle_diff >= Math.PI;
      //Set start of arc
      pathFigure.StartPoint = new Point(center.X + radius * Math.Cos(start_angle), center.Y + radius * Math.Sin(start_angle));
      //set end point of arc.
      arcSegment.Point = new Point(center.X + radius * Math.Cos(end_angle), center.Y + radius * Math.Sin(end_angle));
      arcSegment.Size = new Size(radius, radius);
      arcSegment.SweepDirection = SweepDirection.Clockwise;
  
      pathFigure.Segments.Add(arcSegment);
      pathGeometry.Figures.Add(pathFigure);
      arc_path.Data = pathGeometry;
      canvas.Children.Add(arc_path);
  }