Merge content from multiple pages into one page

Public Class Form1
 
    Private Sub btnMergePageContent_Click(sender As Object, e As EventArgs) Handles btnMergePageContent.Click
        Dim QP As New DebenuPDFLibraryAX1113.PDFLibrary
        If QP.UnlockKey("...") = 1 Then
            If QP.LoadFromFile("C:\temp\mutli_page_content.pdf", "") = 1 Then
 
                ' Remember the original page count
                Dim pageCount = QP.PageCount()
 
                ' First create a new page at the end of the document
                QP.NewPage()
                QP.SetPageSize("Letter")
 
                ' Measure the height of all the pages (but not the new blank page)
                Dim pageHeight(pageCount) As Double
                For page As Integer = 1 To pageCount
                    QP.SelectPage(page)
                    pageHeight(page - 1) = MeasurePageContentHeight(QP)
                Next
 
                ' Capture all the pages (but not the new blank page)
                Dim captureID(pageCount) As Integer
                For page As Integer = 1 To pageCount
                    ' Capture page 1 each time because the pages are
                    ' removed from the document as they are captured
                    captureID(page - 1) = QP.CapturePage(1)
                Next
 
                ' Set the origin to the top of the page
                QP.SetOrigin(1)
 
                ' Draw pages 6, 1, 3, 5 and then 9
                Dim pagesToDraw() As Integer = {6, 1, 3, 5, 9}
                Dim currentPosition As Double = 0
 
                For thisPageIndex As Integer = 1 To UBound(pagesToDraw)
                    ' Look up the page number in the pagesToDraw array
                    Dim thisPageNumber As Integer = pagesToDraw(thisPageIndex - 1)
 
                    ' Draw the captured page (use the full height)
                    QP.DrawCapturedPage(captureID(thisPageNumber - 1), 0, currentPosition, QP.PageWidth(), QP.PageHeight())
 
                    ' Increase the current position
                    currentPosition = currentPosition + pageHeight(thisPageNumber - 1)
                Next
 
                QP.SaveToFile("C:\temp\content.pdf")
            End If
        End If
    End Sub
    ' Measures the height of the page content in the current measurement units
    Private Function MeasurePageContentHeight(PDFLibrary As DebenuPDFLibraryAX1113.PDFLibrary) As Double
        Dim Result As Double = 0
 
        Dim bmpBytes() As Byte = PDFLibrary.RenderPageToVariant(96, PDFLibrary.SelectedPage, 0)
 
        Dim bmpStream As New System.IO.MemoryStream(bmpBytes)
        Dim BMP As New Bitmap(bmpStream)
 
        ' Lock the bitmap's bits
        Dim rect As New Rectangle(0, 0, BMP.Width, BMP.Height)
        Dim bmpData As System.Drawing.Imaging.BitmapData = BMP.LockBits(rect, _
        Drawing.Imaging.ImageLockMode.ReadOnly, BMP.PixelFormat)
 
        ' Get the address of the first line
        Dim ptr As IntPtr = bmpData.Scan0
 
        Dim foundPixels = False
        Dim row = BMP.Height
 
        ' Declare an array to hold the bytes of the bitmap
        Dim bytes As Integer = Math.Abs(bmpData.Stride) * BMP.Height
        Dim rgbValues(bytes - 1) As Byte
 
        ' Copy the RGB values into the array.
        System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes)
        Dim byteOffset = (BMP.Height - 1) * bmpData.Stride
 
        While (Not foundPixels) And (row > 0)
            row = row - 1
 
            ' Set every third value to 255. A 24bpp image will look red. 
            For counter As Integer = 0 To bmpData.Stride - 1
                If (rgbValues(byteOffset + counter) <> 255) Then
                    foundPixels = True
                End If
            Next
 
            byteOffset = byteOffset - bmpData.Stride
        End While
 
        ' Unlock the bits
        BMP.UnlockBits(bmpData)
 
 
        If (foundPixels) Then
            Result = (PDFLibrary.PageHeight() * row) / BMP.Height()
        End If
 
        MeasurePageContentHeight = Result
    End Function
End Class