VB.NET Print Large Image on Multiple Pages - vb.net

Question

i have a problem printing an large image over multiple Pages. I have scanned A4 Documents with 1-x Pages and they put together as one long image. I have to rescale Image to fit in width on A4 and to print with as many pages as on image are. There ist my code, can't achieve this, printing only first page. Any help woud be aprechiated. Thanks! (i'm a beginner...)
Imports System.Drawing.Printing
Imports System.Drawing.Imaging
Imports System.IO
Public Class Form1
Dim Bmp As Bitmap
dim pageNum As Int32 = 0
Private Sub PrintDocument4_PrintPage(ByVal sender As Object, ByVal e As PrintPageEventArgs) Handles PrintDocument4.PrintPage
Dim WidthRatio As Double = e.MarginBounds.Width / Bmp.Width
Dim maxpagenum As Int32 = Math.Ceiling(Bmp.Height / e.MarginBounds.Height * WidthRatio)
Debug.WriteLine(maxpagenum)
Debug.WriteLine(e.MarginBounds.Height)
Dim piece As New Bitmap(CInt(e.MarginBounds.Width / WidthRatio), CInt(e.MarginBounds.Height / WidthRatio))
Dim dest_rect As New Rectangle(0, 0, CInt(e.MarginBounds.Width / WidthRatio), CInt(e.MarginBounds.Height / WidthRatio))
Using gr As Graphics = Graphics.FromImage(piece)
Dim source_rect As New Rectangle(0, 0, CInt(e.MarginBounds.Width / WidthRatio), CInt(e.MarginBounds.Height / WidthRatio))
For i As Integer = 1 To maxpagenum
source_rect.X = 0
' Copy the piece of the image.
gr.DrawImage(Bmp, dest_rect, source_rect, _
GraphicsUnit.Pixel)
'piece.Save("Bmp" & i & ".jpg", ImageFormat.Bmp)
e.Graphics.DrawImage(piece, 0, source_rect.Y, CInt(piece.Width * WidthRatio), CInt(piece.Height * WidthRatio))
pageNum += 1
source_rect.Y += CInt(e.MarginBounds.Height / WidthRatio)
If pageNum < maxpagenum Then
e.HasMorePages = True
Else
pageNum = 0
End If
Next
End Using
End Sub
Private Sub Button9_Click(sender As Object, e As EventArgs) Handles Button9.Click
If ListBox1.SelectedItem IsNot Nothing Then
Dim selItem As String = ListBox1.SelectedItem.ToString()
Dim fs1 As System.IO.FileStream
fs1 = New System.IO.FileStream(selItem, IO.FileMode.Open, IO.FileAccess.Read)
Bmp = New Bitmap(System.Drawing.Image.FromStream(fs1))
fs1.Close()
PrintDocument4 = New PrintDocument
With PrintDialog1
.AllowCurrentPage = False
.AllowPrintToFile = False
.AllowSelection = False
.AllowSomePages = False
.Document = PrintDocument4
.PrinterSettings.DefaultPageSettings.Margins.Top = 15
.PrinterSettings.DefaultPageSettings.Margins.Bottom = 15
.PrinterSettings.DefaultPageSettings.Margins.Left = 15
.PrinterSettings.DefaultPageSettings.Margins.Right = 15
End With
If PrintDialog1.ShowDialog = DialogResult.OK Then
PrintDocument4.PrinterSettings = PrintDialog1.PrinterSettings
AddHandler PrintDocument4.PrintPage, AddressOf PrintDocument4_PrintPage
PrintDocument4.Print()
End If
End If
End Sub