'定义全局变量
Dim BMP As Bitmap '创建的bmp对象
Dim BMPGraphics As Graphics '获得bmp对象的绘制graphic对象
'===============
'在窗体初始化时创建bmp对象,并与picturebox对象关联
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'创建bmp对象,大小和picturebox对象一致
BMP = New Bitmap(PictureBox1.Width, PictureBox1.Height)
'获得bmp对象的graphics
BMPGraphics = Graphics.FromImage(BMP)
'将picturebox的Image对象与bmp对相关联
PictureBox1.Image = BMP
End Sub