vb 把image1和image2合拼成一张图片

image1在底层，image2在顶层，然后图片另存为到命名为123.bmp到C盘根目录里

我是vb新手，老师布置作业，给个全代码谢谢

 Public Class Form1

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim ofn As New OpenFileDialog
        ofn.ShowDialog()
        Dim img1 = Image.FromFile(ofn.FileName)
        ofn.ShowDialog()
        Dim img2 = Image.FromFile(ofn.FileName)
        Dim g = Graphics.FromImage(img1)
        g.DrawImage(img2, New Point() With {.X = 100, .Y = 100})
        img1.Save("123.bmp")
    End Sub
End Class

效果