用vb做的一个带有验证码识别的登陆界面

新建工程，添加一个picturebox，一个textbox，两个command button

Dim vCode As String
Private Sub Command1_Click()
drawvc
End Sub
Private Sub drawvc() ''显示校验码

Dim i, vc, px, py As Long
Dim r, g, b As Byte
Randomize ''初始化随机种子
''生成随机校验码
vc = CLng(8999 * Rnd + 1000)
vCode = vc
''显示校验码
Picture1.Cls
Picture1.Print vc
''添加噪点（防止自动图像识别）
For i = 0 To 2000 ''画2000个噪点
''画点随机位置
px = CLng(Picture1.Width * Rnd)
py = CLng(Picture1.Height * Rnd)
''画点随机颜色
r = CByte(255 * Rnd)
g = CByte(255 * Rnd)
b = CByte(255 * Rnd)
Picture1.Line (px, py)-(px + 1, py + 1), RGB(r, g, b)
Next

End Sub

Private Sub Command2_Click()
If Text1.Text = vCode Then
MsgBox ("正确")
Else
MsgBox ("错误")
drawvc
End If
End Sub

Private Sub Form_Load()
Picture1.FontSize = 12
Picture1.FontBold = True
Picture1.AutoRedraw = True
drawvc
End Sub