Private Sub MakeTransparent_Example1(ByVal e As PaintEventArgs)

    ' Create a Bitmap object from an image file.
    Dim myBitmap As New Bitmap("Grapes.gif")

    ' Draw myBitmap to the screen.
    e.Graphics.DrawImage(myBitmap, 0, 0, myBitmap.Width, _
    myBitmap.Height)

    ' Make the default transparent color transparent for myBitmap.
    myBitmap.MakeTransparent()

    ' Draw the transparent bitmap to the screen.
    e.Graphics.DrawImage(myBitmap, myBitmap.Width, 0, myBitmap.Width, _
    myBitmap.Height)
End Sub

Private Sub MakeTransparent_Example2(ByVal e As PaintEventArgs)

    ' Create a Bitmap object from an image file.
    Dim myBitmap As New Bitmap("Grapes.gif")

    ' Draw myBitmap to the screen.
    e.Graphics.DrawImage(myBitmap, 0, 0, myBitmap.Width, _
        myBitmap.Height)

    ' Get the color of a background pixel.
    Dim backColor As Color = myBitmap.GetPixel(1, 1)

    ' Make backColor transparent for myBitmap.
    myBitmap.MakeTransparent(backColor)

    ' Draw the transparent bitmap to the screen.
    e.Graphics.DrawImage(myBitmap, myBitmap.Width, 0, myBitmap.Width, _
        myBitmap.Height)
End Sub

' 导入命名空间
Imports System.Windows.Forms
Imports System.Drawing
Imports System.Drawing.Drawing2D
public class MakeTransparentBitmap
   public Shared Sub Main
        Application.Run(New Form1)
   End Sub
End class

Public Class Form1
    Inherits System.Windows.Forms.Form

    Private Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Click
        Me.Close()
    End Sub

    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        Dim bm As Bitmap = new Bitmap("yourfile.jpg")

        bm.MakeTransparent(bm.GetPixel(1, 1))

        e.Graphics.DrawImage(bm, 0, 0)
    End Sub
End Class