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实现要点说明：

1. 使用固定宽度字体保证字符对齐
2. 通过空格和星号的组合构建图形轮廓
3. 数学公式控制图形形状：

平行四边形：每行偏移量递减

菱形：分上下半区分别处理星号数量

等腰三角形：星号数量呈奇数增长

4. 坐标计算采用20像素行距确保可读性
5. 所有图形使用相同绘图上下文保证一致性

Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint

Dim g As Graphics = e.Graphics

Dim font As New Font("Courier New", 12)

Dim brush As New SolidBrush(Color.Black)

' 平行四边形（5行9列）

For i As Integer = 0 To 4

Dim line As String = New String(" "c, 4 - i) & New String("*"c, 9)

g.DrawString(line, font, brush, 20, 20 + i * 20)

Next

' 菱形（5行）

Dim space As Integer = 4

Dim star As Integer = 1

For i As Integer = 0 To 4

Dim line As String = New String(" "c, space) & New String("*"c, star)

g.DrawString(line, font, brush, 150, 20 + i * 20)

If i < 2 Then

space -= 1

star += 2

Else

space += 1

star -= 2

End If

Next

' 等腰三角形（5行）

For i As Integer = 0 To 4

Dim line As String = New String(" "c, 4 - i) & New String("*"c, 2 * i + 1)

g.DrawString(line, font, brush, 280, 20 + i * 20)

Next

End Sub