Why is this not showing any results in PictureBox? - vb.net

Question

I'm trying to change an image to black and white on a variable threshold for use in an ocr program. My problem is that I'm not seeing any results in the image that is supposedly processed. I do experience a small wait when rendering, so i am to assume that it is actually doing something.
Imports System.Object
Imports System.Drawing.Bitmap
Public Class Form1
Dim x As Integer, y As Integer
Dim imgx As Integer, imgy As Integer
Dim img As Bitmap
Dim thresh As Bitmap
Dim pixelColor As Color
Dim threshcolor As Color
Dim tempcolor As Color
Public Function getpixel(ByRef x As Integer, ByRef y As Integer) As Color
End Function
Public Sub find_img_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles find_img.Click
open_img.ShowDialog()
img_dsp.Text = open_img.FileName()
img_loc.Text = open_img.FileName
img_dsp.ImageLocation = img_dsp.Text
End Sub
Public Sub find_img_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles find_img.LostFocus
img = (img_dsp.Image)
img_dsp.Refresh()
img_dsp.Text = open_img.FileName()
img_dsp.ImageLocation = img_dsp.Text
img = (img_dsp.Image)
img_dsp.Refresh()
End Sub
Public Sub render_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles render.Click
Dim myx As Integer
Dim myy As Integer
img_threshold.Image = img
thresh = img_threshold.Image
For myy = 1 To (img.Height - 1)
For myx = 1 To (img.Width - 1)
tempcolor = img.GetPixel(myx, myy)
If tempcolor.GetBrightness < NumericUpDown1.Value Then
thresh.SetPixel(x, y, Color.Black)
End If
If tempcolor.GetBrightness > NumericUpDown1.Value Then
thresh.SetPixel(x, y, Color.White)
End If
Next myx
Next myy
img_threshold.Image = thresh
img_threshold.Refresh()
End Sub
End Class

Answer 1

Do you know what a reference is? writing A = B, and changing A and writing B = A?
if you specify that A and B point the same object (a reference to the same object) changing one changes the other too, they occupy the same storage in memory! Teach yourself basic, before writing programs, please.