WPF and its counter-part (WinForms)

Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.IO
Imports System.Windows.Media.Imaging ' xxx
Imports System.Windows.Media         ' xxx
Imports System.Windows
Imports System.ComponentModel
Imports System.Threading

Class ImagesCreation
    ''' <summary>
    ''' Resolutions of the pictures that the Logon UI is going to look for.
    ''' Note : the vertical wallpapers are useful for portrait screens (i.e Tablet PCs, ...) '     { 1280, 1024 },
    ''' </summary>
    Public Shared imgResolutions As Integer(,) = New Integer(,) {{1280, 960}, {1024, 768}, {1600, 1200}, {1440, 900}, {1920, 1200}, {1280, 768}, _
        {1360, 768}, {1024, 1280}, {960, 1280}, {900, 1440}, {768, 1280}, {768, 1360}}
    ''' <summary>
    ''' Path of the original picture
    ''' </summary>
    Private imgPath As String
    Public Sub New(imgPath As String)
        Me.imgPath = imgPath
    End Sub
    ''' <summary>
    ''' Creates the background at each supported resolution
    ''' </summary>
    ''' <param name="sender"></param>
    ''' <param name="args"></param>
    Public Sub run(sender As Object, args As DoWorkEventArgs)
        Thread.Sleep(200)
        Dim bgWorker As BackgroundWorker = TryCast(sender, BackgroundWorker)
        Try
            Dim bmpSrc As New CachedBitmap(New BitmapImage(New Uri(imgPath)), BitmapCreateOptions.None, BitmapCacheOption.OnLoad)                  ' xxx
            For i As Integer = 0 To imgResolutions.GetLength(0) - 1
                Dim w As Integer = imgResolutions(i, 0)
                Dim h As Integer = imgResolutions(i, 1)
                createImage(bmpSrc, w, h, "background" & w & "x" & h & ".jpg")                        ' xxx
                bgWorker.ReportProgress(i + 1)
            Next
            Dim screenWidth As Integer = CInt(Math.Truncate(SystemParameters.PrimaryScreenWidth))
            Dim screenHeight As Integer = CInt(Math.Truncate(SystemParameters.PrimaryScreenHeight))
            createImage(bmpSrc, screenWidth, screenHeight, "backgroundDefault.jpg")                                   ' xxx
                ' 100 means we have finished, no userState parameter means the operation has been successful
            bgWorker.ReportProgress(100)
        Catch ex As Exception
                ' userState parameter has been defined -> operation failed
            bgWorker.ReportProgress(100, ex)
        End Try
    End Sub
    ''' <summary>
    ''' Creates a jpg file which is as close as sub 256kb as possible. (262144 bytes)
    ''' Truncates it if the ratio is not the same as the resolution needed
    ''' </summary>
    ''' <param name="bmpSrc">original bitmap</param>
    ''' <param name="w">Width</param>
    ''' <param name="h">Height</param>
    ''' <param name="filename">destination file name</param>
    Private Sub createImage(bmpSrc As BitmapSource, w As Integer, h As Integer, filename As String)                                     ' xxx
        Dim srcW As Integer = bmpSrc.PixelWidth         ' xxx
        Dim srcH As Integer = bmpSrc.PixelHeight        ' xxx
        Dim ratioSrc As Double = CDbl(srcW) / srcH
        Dim ratioDest As Double = CDbl(w) / h
        Dim newW As Integer
        Dim newH As Integer
        If ratioDest < ratioSrc Then
            newH = srcH
            newW = CInt(Math.Truncate(srcW / ratioSrc * ratioDest))
        Else
            newW = srcW
            newH = CInt(Math.Truncate(srcH * ratioSrc / ratioDest))
        End If
        Dim bmp As New CroppedBitmap(bmpSrc, New Int32Rect((srcW - newW) \ 2, (srcH - newH) \ 2, newW, newH))     ' xxx
        Dim drawingVisual As New DrawingVisual()     ' xxx
        Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()   ' xxx
        drawingContext.DrawImage(bmp, New Rect(0, 0, w, h))   ' xxx
        drawingContext.Close()                                ' xxx
        'Allows us to do a bitmap rendering of a WPF Visual
        Dim tg As New RenderTargetBitmap(w, h, 96, 96, PixelFormats.Pbgra32) ' xxx
        tg.Render(drawingVisual)                                             ' xxx
        Dim found As Boolean = False
        'has the best quality possible been found?
        Dim ms As MemoryStream = Nothing
        Dim quality As Integer = 94
        Dim [step] As Char = "d"C
        'd = decrease quality, i = increase, e = end
        Dim delta As Integer = -8
        Dim topInterval As Integer = 101
        While Not found
            If ms IsNot Nothing Then
                ms.Close()
            End If
            ms = New MemoryStream()
            Dim encoder As New JpegBitmapEncoder()    ' xxx?
            quality += delta
            encoder.QualityLevel = quality
            encoder.Frames.Add(BitmapFrame.Create(tg)) ' xxx
            encoder.Save(ms)
            Dim pos As Long = ms.Position
            If pos < 256 * 1000 Then
                'the image file size is small enough
                If quality = 100 Then
                    found = True
                ElseIf [step] = "d"C Then
                    ' maybe we decreased the quality too much
                    delta = Math.Max(1, Math.Abs(delta \ 2))
                        ' increasing quality
                    [step] = "i"C
                ElseIf [step] = "i"C Then
                    delta = Math.Max(1, Math.Abs(delta \ 2))
                    If delta = 1 AndAlso topInterval = quality + delta Then
                        found = True
                    End If
                ElseIf [step] = "e"C Then
                    'finished
                    found = True
                End If
            Else
                'the image file size is too big
                If [step] = "i"C AndAlso delta = 1 Then
                    ' quality is just 1 unit above the best quality
                    ' we can afford to keep a sub 256kb image
                    [step] = "e"C
                    ' the search of the best quality is finished
                    delta = -1
                ElseIf delta <> -8 Then
                    delta = -Math.Max(1, Math.Abs(delta \ 2))
                    [step] = "d"C
                End If
                    ' if delta == initial delta (-8) -> we haven't increased yet, we can continue descreasing with a large delta
                topInterval = quality
            End If
        End While
        'writes the file : may fail if the user has not the right to create a file. In this case an exception
        'will be thrown and catched by the application. The user will then be prompted by an UAC window, and the operation
        'will be launched again.
        ms.Position = 0
        Dim folder As String = Environment.GetFolderPath(Environment.SpecialFolder.System) & "\oobe\info\backgrounds\"
        If Not Directory.Exists(folder) Then
            Directory.CreateDirectory(folder)
        End If
        Dim fs As New FileStream(folder & filename, FileMode.OpenOrCreate, FileAccess.Write)
        fs.SetLength(0)
        'truncates the file if it already exists
        Dim octet As Integer
        While (InlineAssignHelper(octet, ms.ReadByte())) <> -1
            fs.WriteByte(CByte(octet))
        End While
        fs.Close()
        ms.Close()
    End Sub
    Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, value As T) As T
        target = value
        Return value
    End Function
End Class