请问一个圆角矩形的问题。
这是一个获取圆角的的函数：
Public Shared Function get圆角矩形(ByVal rec As Rectangle, ByVal r As Integer) As Drawing2D.GraphicsPath
Dim gp As New Drawing2D.GraphicsPath
gp.AddLine(rec.Left + r, rec.Top, rec.Right - r, rec.Top) '上
gp.AddArc(rec.Right - r * 2, rec.Top, r * 2, r * 2, 270, 90) '右上
gp.AddLine(rec.Right, rec.Top + r, rec.Right, rec.Bottom - r) '右
gp.AddArc(rec.Right - r * 2, rec.Bottom - r * 2, r * 2, r * 2, 0, 90) '右下
gp.AddLine(rec.Right - r, rec.Bottom, rec.Left + r, rec.Bottom) '下
gp.AddArc(rec.Left, rec.Bottom - r * 2, r * 2, r * 2, 90, 90) '左下
gp.AddLine(rec.Left, rec.Bottom - r, rec.Left, rec.Top + r) '左
gp.AddArc(rec.Left, rec.Top, r * 2, r * 2, 180, 90) '左上
gp.CloseFigure()

Return gp

使用时：
Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
MyBase.OnPaint(e)

Dim rec As New Rectangle(20, 20, 100, 60)
Dim gp As Drawing2D.GraphicsPath = Form1.get圆角矩形(rec, 4)
e.Graphics.FillPath(Brushes.Red, gp)

End Sub


四个角的大小并不一致，特别是当半径小于6左右时，很明显。
请高手指点一下好吗？


[解决办法]
使用 点 的误差问题吧



[解决办法]
误差，没办法，就像在特定分辨率下的圆永远化不圆（不连续，类似下面的效果）
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Public Shared Function get圆角矩形(ByVal rec As Rectangle, ByVal r As Integer) As Drawing2D.GraphicsPath
Dim gp As New Drawing2D.GraphicsPath
gp.AddLine(rec.Left + r, rec.Top, rec.Right - r, rec.Top) '上
gp.AddArc(rec.Right - r * 2, rec.Top, r * 2, r * 2, 270, 90) '右上
gp.AddLine(rec.Right, rec.Top + r, rec.Right, rec.Bottom - r) '右
gp.AddArc(rec.Right - r * 2, rec.Bottom - r * 2, r * 2, r * 2, 0, 90) '右下
gp.AddLine(rec.Right - r, rec.Bottom, rec.Left + r, rec.Bottom) '下

gp.AddArc(rec.Left, rec.Bottom - r * 2, r * 2, r * 2, 90, 90) '左下
gp.AddLine(rec.Left, rec.Bottom - r, rec.Left, rec.Top + r) '左
gp.AddArc(rec.Left, rec.Top, r * 2, r * 2, 180, 90) '左上
gp.CloseFigure()

Return gp

End Function

Private Function CreateRoundedRectPath(ByVal rect As Rectangle, ByVal radius As Integer) As System.Drawing.Drawing2D.GraphicsPath
Dim RoundRect As New System.Drawing.Drawing2D.GraphicsPath

RoundRect.AddLine(rect.Left + radius - 2, rect.Top - 1, rect.Right - radius, rect.Top - 1) '顶端
RoundRect.AddArc(rect.Right - radius, rect.Top - 1, radius, radius, 270, 90) '右上角
RoundRect.AddLine(rect.Right, rect.Top + radius, rect.Right, rect.Bottom - radius) '右边
RoundRect.AddArc(rect.Right - radius, rect.Bottom - radius, radius, radius, 0, 90) '右下角
RoundRect.AddLine(rect.Right - radius, rect.Bottom, rect.Left + radius, rect.Bottom) '底边
RoundRect.AddArc(rect.Left - 1, rect.Bottom - radius, radius, radius, 90, 90) '左下角
RoundRect.AddLine(rect.Left - 1, rect.Top + radius, rect.Left - 1, rect.Bottom - radius) '左边
RoundRect.AddArc(rect.Left - 1, rect.Top - 1, radius, radius, 180, 90) '左上角

Return RoundRect
End Function


Private Function GetRoundedRectPath(ByVal rect As Rectangle, ByVal radius As Integer) As System.Drawing.Drawing2D.GraphicsPath
rect.Offset(-1, -1)
Dim RoundRect As New Rectangle(rect.Location, New Size(radius - 1, radius - 1))
Dim path As New System.Drawing.Drawing2D.GraphicsPath

path.AddArc(RoundRect, 180, 90) '左上角

RoundRect.X = rect.Right - radius '右上角
path.AddArc(RoundRect, 270, 90)

RoundRect.Y = rect.Bottom - radius '右下角
path.AddArc(RoundRect, 0, 90)

RoundRect.X = rect.Left '左下角
path.AddArc(RoundRect, 90, 90)

path.CloseFigure()

Return path
End Function


Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
MyBase.OnPaint(e)

Dim rec As New Rectangle(20, 20, 100, 60)
Dim rec1 As New Rectangle(20, 100, 100, 60)
Dim rec2 As New Rectangle(20, 180, 100, 60)
Dim gp As Drawing2D.GraphicsPath = get圆角矩形(rec, 5)
Dim gp1 As Drawing2D.GraphicsPath = GetRoundedRectPath(rec1, 10)
Dim gp2 As Drawing2D.GraphicsPath = CreateRoundedRectPath(rec2, 10)
e.Graphics.FillPath(Brushes.Red, gp)
e.Graphics.FillPath(Brushes.Red, gp1)
e.Graphics.FillPath(Brushes.Red, gp2)

End Sub
[解决办法]
我也试过了，的确不圆。如果程序没问题的话那也没办法了。
建议手动的设置下几个角的偏移量吧，程序不对称就算了，看上去圆就可以了。