Fastest way to generate thumbnails.

[adrian1906]

Hello,

I'm looking for suggestions on the fastest way to generate thumbnails using VB.net and multiple computers without bogging down the UI.

Right now I have 3 computers and I run an instance of my thumbnail generator code on each. One computer hosts the images. The other two computers access the folder of images via the network.

My code is written to compare the main folder and a thumbnail folder to see if new thumbnails need to be generated. If so, a thread is generated and the thumbnail generation code is ran on the thread. There are 5 threads created in all. So, theoretically, across 3 machines, I'm getting 5 independent threads and I'm thinking that Windows 7 automatically spreads the load across the local cores. In an effort to avoid duplicating work, the comparison is done before the generation of each thumbnail.


This method is faster than using only one computer but drags down the performance on all computers (THE UI also becomes unresponsive). I'm looking for a better way to 1.) Produce the thumbnails as fast as possible 2.) Keep all UI's responsive (boy possibly controlling the priority setting) and 3.) Done within a single instance of the program.

In the #3, I mentioned that I would like to use one instance. Is it possible for networking information be used by the hosting computer that will allow threads to run on the other 2 computers? This way, the 15 threads will be controlled by a single host computer.

Here is a snippet of my code:

    Public Sub CreateThumbsFUNCTION(ByVal IMAGE As String, ByVal MAXDIMENSION As Integer)
        'following code resizes picture to fit.
        'IMAGE needs the full path
        'If thumbnail already exists, it will skip
        Dim newimage As System.Drawing.Image
        Dim EW As New ExifWorks(IMAGE)
        Dim OUTPUTPATH As String() = ExtractPath(IMAGE) ' Note, the '\' is returned
        Dim NewOutputPath As String = OUTPUTPATH(0) & "thumbs_MIS\"
        If File.Exists(NewOutputPath & OUTPUTPATH(1)) Then
            ' do nothing
        Else
            Dim CreateFlagg As Integer = 1
            Dim Hout, Wout As Integer
            newimage = Rotate_Image_From_EXIF(IMAGE)
            Dim bm As New Bitmap(newimage)
                       If bm.Height < MAXDIMENSION And bm.Width < MAXDIMENSION Then
                Hout = bm.Height
                Wout = bm.Width
            Else
                If bm.Height > bm.Width Then
                    Hout = MAXDIMENSION
                    Wout = Hout * (bm.Width / bm.Height)
                Else
                    Wout = MAXDIMENSION
                    Hout = Wout * (bm.Height / bm.Width)
                End If
            End If

            Dim thumb As New Bitmap(Wout, Hout) ' New object for smaller image
            Dim g As Graphics = Graphics.FromImage(thumb)
            g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
            g.DrawImage(bm, New Rectangle(0, 0, Wout, Hout), New Rectangle(0, 0, bm.Width, _
            bm.Height), GraphicsUnit.Pixel)
            g.Dispose()

            'MsgBox(Directory.Exists(NewOutputPath))
            If Directory.Exists(NewOutputPath) = False Then
                Directory.CreateDirectory(NewOutputPath)
            End If
            'MsgBox(NewOutputPath & OUTPUTPATH(1))
            Try
                thumb.Save(NewOutputPath & OUTPUTPATH(1), System.Drawing.Imaging.ImageFormat.Jpeg) 'can use any image format 
                bm.Dispose()
                thumb.Dispose()
                newimage.Dispose()
                EW.Dispose()
            Catch ex As Exception
                msgbox(ex.text)
            End Try
        End If
    End Sub

Thanks,
Adrian