VB API 之 第九课 图像编程(二)

用到2个API函数，Polyiine,Polylineto函数原型如下

Declare Function Polyline Lib "gdi32" Alias "Polyline" (ByVal hdc As Long, lpPoint As POINTAPI, ByVal nCount As Long) As Long
Declare Function PolylineTo Lib "gdi32" Alias "PolylineTo" (ByVal hdc As Long, lppt As POINTAPI, ByVal cCount As Long) As Long

功能说明

　　用来绘制线段

参数

hdc： Long   //设备的句柄

lpPoint　　指向一个POINTAPI的结构。

nCount：Long   //lpPoint数组的点数。

示例：

Option Explicit

Private Declare Function Polyline Lib "gdi32" (ByVal hdc As Long, lpPoint As point, ByVal nCount As Long) As Long
Private Declare Function PolylineTo Lib "gdi32" (ByVal hdc As Long, lppt As point, ByVal cCount As Long) As Long
Private Type point
    x As Long
    y As Long
End Type
    


Dim Flag1 As Boolean
Dim Flag2 As Boolean

Dim Pos(10) As point
Dim i As Integer


Private Sub Command1_Click()
    Flag1 = True
    Flag2 = False
End Sub

Private Sub Command2_Click()
    Flag1 = False
    Flag2 = True
End Sub

Private Sub Command3_Click()
    Flag1 = False
    Flag2 = False
End Sub

Private Sub Command4_Click()
    Me.Picture1.Cls
End Sub

Private Sub Form_Load()
    Flag1 = False
    Flag1 = 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 Flag1 Then
        Pos(i).x = x
        Pos(i).y = y
    If (i >= 3) Then
        Polyline Me.Picture1.hdc, Pos(0), 4
        Me.Picture1.Circle (x, y), 3
        i = 0
        Exit Sub
    End If
End If
'利用PolyLine函数绘图

If Flag2 Then
    Pos(i).x = x
    Pos(i).y = y
    If (i >= 3) Then
        PolylineTo Me.Picture1.hdc, Pos(0), 3
        Me.Picture1.Circle (x, y), 3
        i = 0
        Exit Sub
    End If
End If
'利用PolyLineTo函数绘图
If (i <= 3) Then
    i = i + 1
    Me.Picture1.Circle (x, y), 3
End If
End Sub