如何绘制一个动态的流动管道（FlowPipe）？

分两步绘制

1. 定义属性；
2. 画布重绘；

主要技能：

• 管道的绘制（渐变色矩形）

  /// 

  /// 画渐变色矩形的方法
  /// 
  /// 画布
  /// 画刷
  /// 笔
  /// 矩形
  private void PaintRectangle(Graphics g, Brush brush, Pen pen, Rectangle rectangle)
  {
      //填充矩形
      g.FillRectangle(brush, rectangle);

      switch (this.pipeStyle)
      {
          case PipeStyle.Horizontal:
              g.DrawLine(pen, rectangle.X, rectangle.Y, rectangle.X + rectangle.Width, rectangle.Y);
              g.DrawLine(pen, rectangle.X, rectangle.Y + rectangle.Height - 1, rectangle.X + rectangle.Width, rectangle.Height);
              break;
          case PipeStyle.Vertical:
              g.DrawLine(pen, rectangle.X, rectangle.Y, rectangle.X, rectangle.Y + rectangle.Height);
              g.DrawLine(pen, rectangle.X + rectangle.Width - 1, rectangle.Y, rectangle.X + rectangle.Width - 1, rectangle.Height);
              break;
          default:
              break;
      }
  }

• 管道的绘制（渐变色半圆）

/// 

/// 画渐变色半圆的方法
/// 
/// 画布
/// 
/// 
/// 
/// 
/// 
private void PaintEllipse(Graphics g, ColorBlend colorBlend, Pen p, Rectangle rect, float startAngle, float sweepAngle)
{
    //第一步：创建GPI路径
    GraphicsPath path = new GraphicsPath();
    path.AddEllipse(rect);

    //第二步：渐变色填充
    PathGradientBrush brush = new PathGradientBrush(path);
    brush.CenterPoint = new Point(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);
    brush.InterpolationColors = colorBlend;

    //第三步：绘制管道
    g.FillPie(brush, rect, startAngle, sweepAngle);

    //第四步：绘制边线
    g.DrawArc(p, rect, startAngle, sweepAngle);
}

• 流动条的绘制（用笔的虚线）

//画虚线，关键用笔和路径来画
Pen pen = new Pen(this.flowColor, this.flowWidth);
pen.DashStyle = DashStyle.Custom;
pen.DashPattern = new float[]
{
    flowLength,flowLengthGap
};
pen.DashOffset = this.startOffset;
g.DrawPath(pen, path);

 //流动条路径
 GraphicsPath path = new GraphicsPath();

 //虚线路径—左边、中间、右边
 switch (this.pipeTurnLeft)
 {
     case PipeTurn.Up:
         path.AddArc(new Rectangle(this.Height / 2, this.Height / 2 * (-1) -1, this.Height, this Height), 181.0f, -91.0f);
         break;
     case PipeTurn.Down:
         path.AddArc(new Rectangle(this.Height / 2, this.Height / 2, this.Height, this.Height), 180.0f, 90.0f);
         break;
     default:
         path.AddLine(-1, this.Height / 2, this.Height+1, this.Height / 2);
         break;
 }

• 关键理解：绘制的椭圆、线（Rectangle）的坐标】,宽，高，开始角度，扫描角度>理解了就好画了
  path.AddArc(new Rectangle(this.Height / 2, this.Height / 2, this.Height, this.Height), 180.0f, 90.0f);
path.AddLine(-1, this.Height / 2, this.Height+1, this.Height / 2);

• 可以流动的关键要素

     //流动条流动速度（刷新速度）
     this.myTimer = new Timer();
     myTimer.Interval = 50;
     this.myTimer.Tick += MyTimer_Tick; ;

 }

 #region 定时循环
 private void MyTimer_Tick(object sender, EventArgs e)
 {
     this.startOffset = this.startOffset - this.moveSpeed;

     if (this.startOffset > this.flowLength + this.flowLengthGap || this.startOffset < (this.flowLength + this.flowLengthGap) * (-1))
     { this.startOffset = 0; }
     this.Invalidate();
 }

 #endregion

1.定义属性

• 管道的（两端转向、样式、边沿颜色、中间颜色、激活）
• 流动条的（速度、长度、宽度、间隙、颜色）

//属性示例：按照示例添加以上各种属性
private float moveSpeed = 0.3f;
[Browsable(true)]
[Category("布局_G")]
[Description("流动条速度，负数为反向")]  //属性说明
public float MoveSpeed
{
    get { return moveSpeed; }
    set
    {
        this.moveSpeed = value;
        this.Invalidate();  //重绘
    }
}

2.画布重绘

【管道分为左、中、右三部分。先画管道（矩形）：左、中、右；再画流动条（虚线）：左、中、右】
//矩形画刷
LinearGradientBrush linearGradientBrush = new LinearGradientBrush(new Point(0, 0), new Point(0, this.Height), pipeColorEdge, pipeColorEdge);
linearGradientBrush.InterpolationColors = colorBlend;

//绘制左部分
switch (this.pipeTurnLeft)
{
    case PipeTurn.Up:
        this.PaintEllipse(g, colorBlend, p, new Rectangle(0, this.Height * (-1)-1, this.Height * 2, this.Height * 2), 90.0f, 90.0f);
        break;
    case PipeTurn.Down:
        this.PaintEllipse(g, colorBlend, p, new Rectangle(0, 0, this.Height * 2, this.Height * 2), 180.0f, 90.0f);
        break;
    default:
        this.PaintRectangle(g, linearGradientBrush, p, new Rectangle(-1, 0, this.Height+1, this.Height));
        break;
}

//绘制右部分
switch (this.pipeTurnRight)
{
    case PipeTurn.Up:
        this.PaintEllipse(g, colorBlend, p, new Rectangle(this.Width - this.Height * 2, this.Height * (-1)-1, this.Height * 2, this.Height * 2), 0.0f, 90.0f);
        break;
    case PipeTurn.Down:
        this.PaintEllipse(g, colorBlend, p, new Rectangle(this.Width - this.Height * 2, 0, this.Height * 2, this.Height * 2), 270.0f, 90.0f);
        break;
    default:
        this.PaintRectangle(g, linearGradientBrush, p, new Rectangle(this.Width - this.Height, 0, this.Height, this.Height));
        break;
}

//绘制中间
if (this.Width > this.Height * 2)
{
    this.PaintRectangle(g, linearGradientBrush, p, new Rectangle(this.Height - 1, 0, this.Width - this.Height * 2 + 2, this.Height));
}

//流动条路径
GraphicsPath path = new GraphicsPath();

//虚线路径—左边
switch (this.pipeTurnLeft)
{
    case PipeTurn.Up:
        path.AddArc(new Rectangle(this.Height / 2, this.Height / 2 * (-1) -1, this.Height, this.Height), 181.0f, -91.0f);
        break;
    case PipeTurn.Down:
        path.AddArc(new Rectangle(this.Height / 2, this.Height / 2, this.Height, this.Height), 180.0f, 90.0f);
        break;
    default:
        path.AddLine(-1, this.Height / 2, this.Height+1, this.Height / 2);
        break;
}

//虚线路径—中间
if (this.Width > this.Height * 2)
{
    path.AddLine(this.Height, this.Height / 2, this.Width - this.Height -1, this.Height / 2);
}

//虚线路径—右边
switch (this.pipeTurnRight)
{
    case PipeTurn.Up:
        path.AddArc(new Rectangle(this.Width - 1 - this.Height * 3 / 2, -this.Height / 2-1 , this.Height, this.Height), 88f, -91.0f);
        break;
    case PipeTurn.Down:
        path.AddArc(new Rectangle(this.Width - 1 - this.Height * 3 / 2, this.Height / 2, this.Height, this.Height), 270.0f, 90.0f);
        break;
    default:
        path.AddLine(this.Width - this.Height, this.Height / 2, this.Width , this.Height / 2);
        break;
}

//画虚线，关键用笔和路径来
Pen pen = new Pen(this.flowColor, this.flowWidth);
pen.DashStyle = DashStyle.Custom;
pen.DashPattern = new float[]
{
    flowLength,flowLengthGap
};
pen.DashOffset = this.startOffset;
g.DrawPath(pen, path);

格式都是一样的，掌握关键代码，肝就对了。

End