Image splicing

Imports System
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Drawing.Imaging
Imports System.collections
Imports System.ComponentModel
Imports System.Windows.Forms
Imports System.data
Imports System.Runtime.InteropServices
 
Public Class Form1
 
    Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click
 
        Dim tif1 As String = "c:\imgtest\004.tif"
        Dim tif2 As String = "c:\imgtest\005.tif"
        Dim tif3 As String = "c:\imgtest\006.tif"
 
        Dim img1 As Image = Image.FromFile(tif1)
        Dim img2 As Image = (Image.FromFile(tif2))
 
        Dim Width As Integer = (img1.Width)
        Dim Height As Integer = (img1.Height + img2.Height)
        Dim img3 As Bitmap = (New Bitmap(Width, Height))
        img3.SetResolution(200, 200)
 
        Dim g As Graphics = (Graphics.FromImage(img3))
 
 
 
        g.Clear(Color.Black)
        g.DrawImage(img1, New Point(0, 0))
        g.DrawImage(img2, New Point(0, img2.Height))
 
        g.Dispose()
        img1.Dispose()
        img2.Dispose()
 
 
        'new code from James
        'lock the bits of the original bitmap
        Dim bmdo As BitmapData = img3.LockBits(New Rectangle(0, 0, img3.Width, img3.Height), ImageLockMode.ReadOnly, img3.PixelFormat)
        'add new 1bpp bitmap and lock its bits
        Dim img4 As Bitmap = New Bitmap(img3.Width, img3.Height, PixelFormat.Format1bppIndexed)
        img4.SetResolution(200, 200)
 
        Dim bmdn As BitmapData = img4.LockBits(New Rectangle(0, 0, img4.Width, img4.Height), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed)
        'scan through the pixels y by x
        Dim y As Integer
        For y = 0 To img3.Height - 1
            Dim x As Integer
            For x = 0 To img3.Width - 1
                'generate address of colour pixel
                Dim index As Integer = y * bmdo.Stride + x * 4
                'check it's brightness
                If Color.FromArgb(Marshal.ReadByte(bmdo.Scan0, index + 2), Marshal.ReadByte(bmdo.Scan0, index + 1), Marshal.ReadByte(bmdo.Scan0, index)).GetBrightness() > 0.5F Then
                    Me.SetIndexedPixel(x, y, bmdn, True)
                End If
            Next
        Next
        'tidy up
        img3.UnlockBits(bmdo)
        img4.UnlockBits(bmdn)
        img3.Dispose()
 
        Dim info As ImageCodecInfo = Nothing
        Dim ice As ImageCodecInfo
        For Each ice In ImageCodecInfo.GetImageEncoders()
            If ice.MimeType = "image/tiff" Then
                info = ice
                Exit For
            End If
        Next
 
 
        Dim enc As Encoder = Encoder.SaveFlag
        Dim ep As New EncoderParameters(1)
 
        ep.Param(0) = New EncoderParameter(Encoder.Compression, CLng(EncoderValue.CompressionCCITT4))
 
 
        img4.Save(tif3, info, ep)
        img4.Dispose()
 
        'end of new code
        MsgBox("Done")
    End Sub
 
    Protected Sub SetIndexedPixel(ByVal x As Integer, ByVal y As Integer, ByVal bmd As BitmapData, ByVal pixel As Boolean)
        Dim index As Integer = y * bmd.Stride + (x >> 3)
        Dim p As Byte = Marshal.ReadByte(bmd.Scan0, index)
        Dim mask As Byte = &H80 >> (x And &H7)
        If pixel Then
            p = p Or mask
        Else
            p = p And CByte(mask ^ &HFF)
        End If
        Marshal.WriteByte(bmd.Scan0, index, p)
    End Sub

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