VB API 之 第十课 图像编程(三)

　　首先绘制多边形的API函数有：

　　Polygon();   //描绘一个多边形，由两点或三点的任意系列构成

　　polyPolygon();   //用当前选定的画笔绘画两个或多个多边形

　　PolyPolyline();   //用当前选定的画笔描绘两个或多个多边形

　　首先来看Polygon的函数原型

Private Declare Function Polygon Lib "gdi32" Alias "Polygon" (ByVal hdc As Long, lpPoint As POINTAPI, ByVal nCount As Long) As Long

　　参数说明

　　hdc： Long  // 绘制多边形设备的句柄

　　lpPoint  //指向一个POINTAPI类型的数组

　　nCount：Long  //多边形的顶点数

　　返回Long类型值，返回0表示失败，不为0则表示成功

Option Explicit

Private Type POINTAPI
    x As Long
    y As Long
End Type

Private Declare Function Polygon Lib "gdi32" (ByVal hdc As Long, lpPoint As POINTAPI, ByVal nCount As Long) As Long
Dim Pos(5) As POINTAPI
Dim Flag As Boolean
Dim i As Integer
'绘图标志变量

Private Sub Command1_Click()
Flag = True
'开始绘图
End Sub

Private Sub Command2_Click()
Flag = False
'结束绘图
End Sub

Private Sub Form_Load()
Flag = False
'禁止绘图
Me.ScaleMode = 3
Me.Picture1.ScaleMode = 3
'设置对象坐标的度量单位为像素
i = 0
End Sub

Private Sub Picture1_MouseUp(Button As Integer, Shift As Integer, x As Single, y As Single)
If Flag Then
Pos(i).x = x
Pos(i).y = y
If (i >= 3) Then
Polygon Me.Picture1.hdc, Pos(0), 4
'将多边形的边数设置为4
'你也可以自己修改多边形的边数
Me.Picture1.Circle (x, y), 3
i = 0
Exit Sub
End If
End If
'绘制多边形
If (i <= 3) Then
i = i + 1
Me.Picture1.Circle (x, y), 3
End If
End Sub