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I've tried to parallelize the resizing of jpegs using .Net. All my tries failed, because the Graphics.DrawImage-func seems to lock while active. Try the following snipped: Sub Main() Dim files As String() = IO.Directory.GetFiles("D:\TEMP") Dim imgs(25) As Image For i As Integer = 0 To 25 imgs(i) = Image.FromFile(files(i)) Next Console.WriteLine("Ready to proceed ") Console.ReadLine() pRuns = 1 For i As Integer = 0 To 25 Threading.Interlocked.Increment(pRuns) Threading.ThreadPool.QueueUserWorkItem(New Threading.WaitCallback(AddressOf LongTerm), imgs(i)) Next Threading.Interlocked.Decrement(pRuns) pSema.WaitOne() Console.WriteLine("Fin") Console.ReadLine() End Sub Sub LongTerm(ByVal state As Object) Dim newImageHeight As Integer Dim oldImage As Image = CType(state, Image) Dim newImage As Image Dim graph As Graphics Dim rect As Rectangle Dim stream As New IO.MemoryStream Try newImageHeight = Convert.ToInt32(850 * oldImage.Height / oldImage.Width) newImage = New Bitmap(850, newImageHeight, oldImage.PixelFormat) graph = Graphics.FromImage(newImage) rect = New Rectangle(0, 0, 850, newImageHeight) With graph .CompositingQuality = Drawing2D.CompositingQuality.HighQuality .SmoothingMode = Drawing2D.SmoothingMode.HighQuality .InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic End With 'Save image to memory stream graph.DrawImage(oldImage, rect) newImage.Save(stream, Imaging.ImageFormat.Jpeg) Catch ex As Exception Finally If graph IsNot Nothing Then graph.Dispose() End If If newImage IsNot Nothing Then newImage.Dispose() End If oldImage.Dispose() stream.Dispose() Console.WriteLine("JobDone {0} {1}", pRuns, Threading.Thread.CurrentThread.ManagedThreadId) Threading.Interlocked.Decrement(p

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