填充路径不填充整个图形路径？

Question

试图填满那个中心区域，不知道我做错了什么。

Imports System.Drawing.Drawing2D

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    End Sub

    Private Sub Form1_Paint(sender As System.Object, e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint
        Dim gp As GraphicsPath = CreatePath(New Rectangle(New Point(200, 200), New Size(250, 100)))
        e.Graphics.FillPath(New SolidBrush(Color.LightBlue), gp)
        e.Graphics.DrawPath(New Pen(Color.Black), gp)

    End Sub

    Private Function CreatePath(ByVal area As Rectangle) As GraphicsPath

        Dim gp As New GraphicsPath()
        Dim rect As Rectangle = New Rectangle(area.Location, New Size(area.Width, area.Height \ 3))
        gp.AddEllipse(rect)

        Dim hadj As Integer = area.Height \ 4
        gp.AddLine(New Point(area.X, area.Y + area.Height - hadj), New Point(area.X, area.Y + (rect.Height \ 3) + 8))

        Dim gh As Integer = area.Width \ 4
        Dim pts(4) As PointF
        pts(0) = New PointF(area.X, area.Y + area.Height - hadj)
        pts(1) = New Point(area.X + gh, area.Y + area.Height - (hadj \ 2))
        pts(2) = New Point(area.X + gh * 2, area.Y + area.Height - (hadj \ 3))
        pts(3) = New Point(area.X + gh * 3, area.Y + area.Height - (hadj \ 2))
        pts(4) = New Point(area.X + area.Width, area.Y + area.Height - hadj)
        gp.AddCurve(pts)

        gp.AddLine(New PointF(area.X + area.Width, area.Y + (rect.Height \ 3) + 9), New PointF(area.X + area.Width, area.Y + area.Height - hadj))
        Return gp
    End Function
End Class

Answer 1

试试下面的。默认情况下，GraphicsPath 使用交替填充模式，交替添加/减去填充。缠绕填充模式使用方向从填充中增加（顺时针）或减少（逆时针）。

Private Function CreatePath(ByVal area As Rectangle) As GraphicsPath
    '* Set fill mode to winding (see FillMode Help)
    Dim gp As New GraphicsPath(FillMode.Winding)

    Dim rect As Rectangle = New Rectangle(area.Location, New Size(area.Width, area.Height \ 3))
    gp.AddEllipse(rect)

    '* Reorder points so that path goes clockwise (see FillMode.Winding Help)

    Dim hadj As Integer = area.Height \ 4
    'Left side bottom -> top
    'gp.AddLine(New Point(area.X, area.Y + area.Height - hadj), New Point(area.X, area.Y + (rect.Height \ 3) + 8))

    '* Right side top -> bottom (clockwise)
    '* NOTE: Top Y value was a bit too high, adjusted by -3.  Adjust calculation or maybe use floating point math and used rounding, ceil, or floor
    gp.AddLine(New PointF(area.X + area.Width, area.Y + (rect.Height \ 3) + 9 - 3), New PointF(area.X + area.Width, area.Y + area.Height - hadj))

    Dim gh As Integer = area.Width \ 4
    Dim pts(4) As PointF
    'pts(0) = New PointF(area.X, area.Y + area.Height - hadj)
    'pts(1) = New Point(area.X + gh, area.Y + area.Height - (hadj \ 2))
    'pts(2) = New Point(area.X + gh * 2, area.Y + area.Height - (hadj \ 3))
    'pts(3) = New Point(area.X + gh * 3, area.Y + area.Height - (hadj \ 2))
    'pts(4) = New Point(area.X + area.Width, area.Y + area.Height - hadj)
    '* Reordered points (clockwise)
    pts(0) = New Point(area.X + area.Width, area.Y + area.Height - hadj)
    pts(1) = New Point(area.X + gh * 3, area.Y + area.Height - (hadj \ 2))
    pts(2) = New Point(area.X + gh * 2, area.Y + area.Height - (hadj \ 3))
    pts(3) = New Point(area.X + gh, area.Y + area.Height - (hadj \ 2))
    pts(4) = New PointF(area.X, area.Y + area.Height - hadj)
    gp.AddCurve(pts)

    'Right side top -> bottom
    'gp.AddLine(New PointF(area.X + area.Width, area.Y + (rect.Height \ 3) + 9), New PointF(area.X + area.Width, area.Y + area.Height - hadj))

    '* Left side bottom -> top (clockwise)
    '* NOTE: Top Y value was a bit too high, adjusted by -2.  Adjust calculation or maybe use floating point math and used rounding, ceil, or floor
    gp.AddLine(New Point(area.X, area.Y + area.Height - hadj), New Point(area.X, area.Y + (rect.Height \ 3) + 8 - 2))

    Return gp
End Function

Answer 2

另一种方法，只是为了展示GraphicsPath对象的Reset()方法。
由于圆柱体可以看作是两个省略号和一个矩形的组合（透视创建了 3D 对象的错觉），因此这里首先填充这些形状，然后是外部部分（形状边框）是独立绘制的。

这最终将允许在需要时为图形使用不同的画笔。

结果示例：

---

Private upperRect As Rectangle = New Rectangle(New Point(10, 10), New Size(180, 80))
Private lowerRect As Rectangle = New Rectangle(New Point(10, 100), New Size(180, 80))

Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles MyBase.Paint
    e.Graphics.SmoothingMode = SmoothingMode.AntiAlias

    Dim middleRect As Rectangle = CylinderMiddleRect(upperRect, lowerRect)

    Using gp As New GraphicsPath(FillMode.Winding)
        gp.AddEllipse(upperRect)
        gp.AddRectangle(middleRect)
        gp.AddEllipse(lowerRect)
        e.Graphics.FillPath(Brushes.LightBlue, gp)
        gp.Reset()

        gp.AddArc(lowerRect, 0, 180)
        gp.AddEllipse(upperRect)
        gp.AddLine(New Point(middleRect.X, middleRect.Y), New Point(upperRect.X, middleRect.Bottom))
        gp.CloseFigure()
        gp.AddLine(New Point(middleRect.Right, middleRect.Y), New Point(middleRect.Right, middleRect.Bottom))
        gp.CloseFigure()
        e.Graphics.DrawPath(Pens.Black, gp)
    End Using
End Sub

Private Function CylinderMiddleRect(upperRect As Rectangle, lowerRect As Rectangle) As Rectangle
    Dim distance = (lowerRect.Y + (lowerRect.Height \ 2)) - (upperRect.Y + (upperRect.Height \ 2))

    Return New Rectangle(New Point(upperRect.X, upperRect.Y + (upperRect.Height \ 2)),
                         New Size(upperRect.Width, distance))
End Function