圆角四边形的绘制

本节内容可以参考文件"\CaseStudy\流程图\纯代码流程图\纯代码绘制之五.Table"

使用GDI+绘制流程的最大的好处是随心所欲，你愿意怎么画都行，无需局限于内置的形状。

例如你想将流程图中的四边形变成圆角的，如下图：

只需在上一节的基础上，将Map控件的OwerDrawMark事件的代码改为：

'定义一个lambda函数，用于计算圆角四边形的路径
Dim CreateRoundedRectanglePath =
Function(tRect As Rectangle, tRadius As Integer)
    Dim tPath As New GraphicsPath()
    tRadius = Math.Min( tRadius, Math.Min(tRect.Width / 2, tRect.Height / 2))
    If tRadius <= 0 Then
        tPath.AddRectangle(tRect)
        Return tPath
    End If
    tPath.AddArc(tRect.X, tRect.Y, tRadius * 2, tRadius * 2, 180F, 90F)
    tPath.AddLine(tRect.X + tRadius, tRect.Y, tRect.Right - tRadius, tRect.Y)
    tPath.AddArc(tRect.Right - tRadius * 2, tRect.Y, tRadius * 2, tRadius * 2, 270F, 90F)
    tPath.AddLine(tRect.Right, tRect.Y + tRadius, tRect.Right, tRect.Bottom - tRadius)
    tPath.AddArc(tRect.Right - tRadius * 2, tRect.Bottom - tRadius * 2, tRadius * 2, tRadius * 2, 0F, 90F)
    tPath.AddLine(tRect.Right - tRadius, tRect.Bottom, tRect.X + tRadius, tRect.Bottom)
    tPath.AddArc(tRect.X, tRect.Bottom - tRadius * 2, tRadius * 2, tRadius * 2, 90F, 90F)
    tPath.AddLine(tRect.X, tRect.Bottom - tRadius, tRect.X, tRect.Y + tRadius)
    tPath.CloseAllFigures()
    Return tPath
End Function
If e.ShapeTag IsNot Nothing AndAlso TypeOf e.ShapeTag Is DataRow Then
    Dim dr As DataRow = e.ShapeTag
    Dim brush As Brush = Brushes.Black
    Dim pen As New Pen(color.Black)
    pen.Width = 2
    Dim rect As Rectangle = Rectangle.Round(e.Bounds)
    Select Case dr("类型")
        Case "四边形"
            Dim rectPath As GraphicsPath = CreateRoundedRectanglePath.Invoke(rect, 10) '10为圆角半径
            Select Case dr("文本")
                Case "开始"
                    e.Graphics.FillPath(Brushes.RoyalBlue, rectPath)
                    brush = Brushes.White
                Case "结束"
                    e.Graphics.FillPath(Brushes.DarkOrchid, rectPath)
                    brush = Brushes.White
                Case Else
                    e.Graphics.DrawPath(pen, rectPath)
            End Select
        Case "菱形"
            Dim p1 As New PointF(rect.X, rect.Y + rect.Height / 2) '左顶点
            Dim p2 As New PointF(rect.X + rect.Width / 2, rect.Y) '上顶点
            Dim p3 As New PointF(rect.X + rect.Width , rect.Y + rect.Height / 2) '右顶点
            Dim p4 As New PointF(rect.X + rect.Width / 2, rect.Y + rect.Height) '下顶点
            e.Graphics.DrawPolygon(pen, {p1, p2, p3, p4}) '绘制菱形
    End Select
    Dim fnt As New Font("微软雅黑", 12)
    Dim fmt As New StringFormat()
    fmt.Alignment = StringAlignment.Center
    fmt.LineAlignment = StringAlignment.Center
    e.Graphics.DrawString(dr("文本"), fnt, brush, rect, fmt)
End If