Public Sub SetThresholdExample(ByVal e As PaintEventArgs)

    ' Open an Image file, and draw it to the screen.
    Dim myImage As Image = Image.FromFile("Camera.jpg")
    e.Graphics.DrawImage(myImage, 20, 20)

    ' Create an ImageAttributes object, and set its color threshold.
    Dim imageAttr As New ImageAttributes
    imageAttr.SetThreshold(0.7F)

    ' Draw the image with the colors bifurcated.
    Dim rect As New Rectangle(300, 20, 200, 200)
    e.Graphics.DrawImage(myImage, rect, 0, 0, 200, 200, _
    GraphicsUnit.Pixel, imageAttr)
End Sub

' 导入命名空间
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms

public class SetThreashold
   public Shared Sub Main
        Application.Run(New Form1)
   End Sub
End class

public class Form1
  Inherits System.Windows.Forms.Form

  Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
        Dim g As Graphics = Me.CreateGraphics()
        g.Clear(Me.BackColor)
        Dim lClr As Color = Color.FromArgb(245, 0, 0)
        Dim uClr As Color = Color.FromArgb(255, 0, 0)
        Dim ImgAttr As New ImageAttributes
        ImgAttr.SetThreshold(0.7F, ColorAdjustType.Default)
        Dim curImage As Image = Image.FromFile("yourfile.jpg")
        g.DrawImage(curImage, 0, 0)
        Dim rect As New Rectangle(0, 0, 400, 400)
        g.DrawImage(curImage, rect, 0, 0, 400, 400, GraphicsUnit.Pixel, ImgAttr)
        ' Dispose
        g.Dispose()


  End Sub

  Public Sub New()
   
    MyBase.New()
    Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
    Me.ClientSize = New System.Drawing.Size(292, 273)
    Me.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen

  End Sub

End Class