透明图像上不透明的拉绳

Question

我想在一个不透明的透明位图上画一个红色的字符串，然后在另一个位图（或表格）上画这个位图。

代码：

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Me.Invalidate()
    End Sub

    Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles Me.Paint
        Dim Img As Bitmap = New Bitmap(300, 300)
        Dim G As Graphics = Graphics.FromImage(Img)
        With G
            .DrawString("SIMPLE TEST!", New Font("Arial", 50), New SolidBrush(Color.FromArgb(50, 255, 0, 0)), New Point(0, 0))
            .Dispose()
        End With
        G = e.Graphics()
        G.DrawImage(Img, New Point(0, 0))
    End Sub
End Class

结果：

显示字符串没有不透明度，而是黑红混合颜色。

如何在透明位图上绘制不透明的字符串？