vb.net graphic 简单的画图程序

 [vb]
Public Class Form1 
    Dim DrawState As Boolean 
    Dim PreX As Single 
    Dim PreY As Single 
    Dim eP As New Pen(Color.Black, 3)          ' 构造黑色画笔，并将它赋给对象变量eP  
    'Dim g As Graphics = Me.CreateGraphics     ' 在窗体上构造一块画布，并将它赋给对象变量g  
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 
        ' 将DrawState初始化为False，表示提笔  
        DrawState = False 
    End Sub 
 
    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown 
        ' 当鼠标左键被按下时，把DrawState设为True，表示落笔开始画线  
        Dim g As Graphics = Me.CreateGraphics 
        If e.Button = Windows.Forms.MouseButtons.Left Then 
            DrawState = True     ' 设置画图状态  
            PreX = e.X          ' PreX和PreY保存了线条的起点。  
            PreY = e.Y 
        End If 
        ' 当按住鼠标右键时，画一个直径为50的圆  
        If e.Button = Windows.Forms.MouseButtons.Right Then 
            g.DrawEllipse(eP, e.X - 25, e.Y - 25, 100, 100) 
        End If 
    End Sub 
 
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove 
        ' 当鼠标移动时，如果处于画线状态，则在(PreX，PreY)与(X，Y)之间画一条直线  
        Dim g As Graphics = Me.CreateGraphics 
        If DrawState = True Then 
            g.DrawLine(eP, PreX, PreY, e.X, e.Y) 
            PreX = e.X 
            PreY = e.Y 
        End If 
 
    End Sub 
 
    Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp 
        ' 当释放鼠标左键时，解除画线状态  
        If e.Button = Windows.Forms.MouseButtons.Left Then 
            DrawState = False 
        End If 
    End Sub 
End Class 

Public Class Form1
    Dim DrawState As Boolean
    Dim PreX As Single
    Dim PreY As Single
    Dim eP As New Pen(Color.Black, 3)          ' 构造黑色画笔，并将它赋给对象变量eP
    'Dim g As Graphics = Me.CreateGraphics     ' 在窗体上构造一块画布，并将它赋给对象变量g

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' 将DrawState初始化为False，表示提笔
        DrawState = False
    End Sub

    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        ' 当鼠标左键被按下时，把DrawState设为True，表示落笔开始画线
        Dim g As Graphics = Me.CreateGraphics
        If e.Button = Windows.Forms.MouseButtons.Left Then
            DrawState = True     ' 设置画图状态
            PreX = e.X          ' PreX和PreY保存了线条的起点。
            PreY = e.Y
        End If
        ' 当按住鼠标右键时，画一个直径为50的圆
        If e.Button = Windows.Forms.MouseButtons.Right Then
            g.DrawEllipse(eP, e.X - 25, e.Y - 25, 100, 100)
        End If
    End Sub

    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        ' 当鼠标移动时，如果处于画线状态，则在(PreX，PreY)与(X，Y)之间画一条直线
        Dim g As Graphics = Me.CreateGraphics
        If DrawState = True Then
            g.DrawLine(eP, PreX, PreY, e.X, e.Y)
            PreX = e.X
            PreY = e.Y
        End If

    End Sub

    Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
        ' 当释放鼠标左键时，解除画线状态
        If e.Button = Windows.Forms.MouseButtons.Left Then
            DrawState = False
        End If
    End Sub
End Class

改法1
 

[vb] 
Public Class Form1 
    Dim DrawState As Boolean 
    Dim PreX As Single 
    Dim PreY As Single 
    Dim eP As New Pen(Color.Black, 3)          ' 构造黑色画笔，并将它赋给对象变量eP  
    Dim g As Graphics     ' 在窗体上构造一块画布，并将它赋给对象变量g  
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 
        ' 将DrawState初始化为False，表示提笔  
        DrawState = False 
    End Sub 
 
    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown 
        ' 当鼠标左键被按下时，把DrawState设为True，表示落笔开始画线  
        'Dim g As Graphics = Me.CreateGraphics  
        If e.Button = Windows.Forms.MouseButtons.Left Then 
            DrawState = True     ' 设置画图状态  
            PreX = e.X          ' PreX和PreY保存了线条的起点。  
            PreY = e.Y 
        End If 
        ' 当按住鼠标右键时，画一个直径为50的圆  
        If e.Button = Windows.Forms.MouseButtons.Right Then 
            g.DrawEllipse(eP, e.X - 25, e.Y - 25, 100, 100) 
        End If 
    End Sub 
 
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove 
        ' 当鼠标移动时，如果处于画线状态，则在(PreX，PreY)与(X，Y)之间画一条直线  
        'Dim g As Graphics = Me.CreateGraphics  
        If DrawState = True Then 
            g.DrawLine(eP, PreX, PreY, e.X, e.Y) 
            PreX = e.X 
            PreY = e.Y 
        End If 
 
    End Sub 
 
    Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp 
        ' 当释放鼠标左键时，解除画线状态  
        If e.Button = Windows.Forms.MouseButtons.Left Then 
            DrawState = False 
        End If 
    End Sub 
 
 
Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize 
        g = Me.CreateGraphics 
    End Sub 
End Class 

Public Class Form1
    Dim DrawState As Boolean
    Dim PreX As Single
    Dim PreY As Single
    Dim eP As New Pen(Color.Black, 3)          ' 构造黑色画笔，并将它赋给对象变量eP
    Dim g As Graphics     ' 在窗体上构造一块画布，并将它赋给对象变量g

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' 将DrawState初始化为False，表示提笔
        DrawState = False
    End Sub

    Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        ' 当鼠标左键被按下时，把DrawState设为True，表示落笔开始画线
        'Dim g As Graphics = Me.CreateGraphics
        If e.Button = Windows.Forms.MouseButtons.Left Then
            DrawState = True     ' 设置画图状态
            PreX = e.X          ' PreX和PreY保存了线条的起点。
            PreY = e.Y
        End If
        ' 当按住鼠标右键时，画一个直径为50的圆
        If e.Button = Windows.Forms.MouseButtons.Right Then
            g.DrawEllipse(eP, e.X - 25, e.Y - 25, 100, 100)
        End If
    End Sub

    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        ' 当鼠标移动时，如果处于画线状态，则在(PreX，PreY)与(X，Y)之间画一条直线
        'Dim g As Graphics = Me.CreateGraphics
        If DrawState = True Then
            g.DrawLine(eP, PreX, PreY, e.X, e.Y)
            PreX = e.X
            PreY = e.Y
        End If

    End Sub

    Private Sub Form1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
        ' 当释放鼠标左键时，解除画线状态
        If e.Button = Windows.Forms.MouseButtons.Left Then
            DrawState = False
        End If
    End Sub

Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
        g = Me.CreateGraphics
    End Sub
End Class