I have a class which I am using to resize a JPG. Apparently, this technique does not give the same file size depending on which environment it sits on. When I execute this on my Windows 8.1, I do not get the same file size as when this is being executed on Windows Server 2008.

    ' Resize an image
    Public Function ImageResize() As Boolean
        Dim lcFile As String = ""
        Dim lnHeightRatio As Integer = 0
        Dim lnRatio As Double = 0
        Dim lnRatioImage As Double = 0
        Dim lnWidthRatio As Integer = 0
        Dim loFinalImage As Bitmap = Nothing
        Dim loGraphics As System.Drawing.Graphics = Nothing
        Dim loImage As System.Drawing.Bitmap = Nothing
        Dim loImage2 As System.Drawing.Bitmap = Nothing

        ' Reset the values
        lImageHasBeenPreserved = False
        oImage = Nothing

        ' Initialization
        lcFile = Trim(cFile)
        lVerifyForWidthAndHeight = True

        ' If the file does not exist
        If Not oApp.FileExist(lcFile) Then
            cMessage = cFileDoesNotExist
            Return False
        End If

        ' Try to negotiate with the image
        Try
            loImage = New System.Drawing.Bitmap(lcFile)
        Catch loError As Exception
            cMessage = oApp.StrTran(cThisFileIsNotSupported, "##File##", lcFile)
            Return False
        End Try

        ' If we can resize with no crop
        If lResizeButNoCrop Then

            ' Calculate the proper ratio as per the width
            lnHeightRatio = nWidth * loImage.Height / loImage.Width

            ' If the height is greater than the targeted resize height
            If lnHeightRatio > nHeight Then

                ' Adjust the width in regards to that
                nWidth = nHeight * loImage.Width / loImage.Height

                ' Use this flag to bypass the validation when the width and height is defined
                lVerifyForWidthAndHeight = False

            Else

                ' Calculate the proper ratio as per the height
                lnWidthRatio = nHeight * loImage.Width / loImage.Height

                ' If the height is greater than the targeted resize height
                If lnWidthRatio > nWidth Then

                    ' Adjust the height in regards to that
                    nHeight = nWidth * loImage.Height / loImage.Width

                    ' Use this flag to bypass the validation when the width and height is defined
                    lVerifyForWidthAndHeight = False

                End If

            End If

        End If

        ' If the image is already with the proper dimensions
        If nWidth = loImage.Width And nHeight = loImage.Height Then
            lImageHasBeenPreserved = True

            ' This is necessary as the image would remain locked
            loImage.Dispose()

            Return True
        End If

        ' If the width calculated is bigger than the original width or if the height calculated if bigger than the original width
        ' This is in the case the original image is 250x250 and that we would want to resize it to 600x900
        ' In such situation, we preserve the original image otherwise it would be deformed
        If nWidth > loImage.Width Or nHeight > loImage.Height Then
            nWidth = loImage.Width
            nHeight = loImage.Height
        End If

        ' Initialize a new image object on the required dimensions
        loImage2 = New System.Drawing.Bitmap(nWidth, nHeight, loImage.PixelFormat)

        ' If we can resize
        If loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Format1bppIndexed Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Format4bppIndexed Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Format8bppIndexed Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Undefined Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.DontCare Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Format16bppArgb1555 Or _
            loImage2.PixelFormat = Drawing.Imaging.PixelFormat.Format16bppGrayScale Then
            cMessage = cPixelFormatNotSupported

            ' This is necessary as the image would remain locked
            loImage.Dispose()

            Return False
        End If

        ' Initialization
        lnRatio = nWidth / nHeight
        lnRatioImage = loImage.Width / loImage.Height

        ' If the ratio of the image is smaller than the calculcated ratio
        If lnRatioImage < lnRatio Then
            nCropWidth = loImage.Width
            nCropHeight = loImage.Width / lnRatio
        Else
            nCropWidth = loImage.Height * lnRatio
            nCropHeight = loImage.Height
        End If

        ' Crop needs it
        oImage = loImage

        ' If we cannot crop
        If Not Crop() Then

            ' This is necessary as the image would remain locked
            loImage.Dispose()

            Return False
        End If

        ' Create the placeholder
        loFinalImage = New Bitmap(nWidth, nHeight)

        ' Assign the placeholder into the graphic converter
        loGraphics = System.Drawing.Graphics.FromImage(loFinalImage)

        ' Set the parameters
        loGraphics.SmoothingMode = Drawing.Drawing2D.SmoothingMode.HighQuality
        loGraphics.InterpolationMode = Drawing.Drawing2D.InterpolationMode.HighQualityBicubic
        loGraphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality
        loGraphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality

        ' Resize the image
        loGraphics.DrawImage(loImage, 0, 0, nWidth, nHeight)

        ' Release the image
        loGraphics.Dispose()

        ' The oImage property can now be assigned to the resized version
        oImage = loFinalImage

        ' If the image has not been altered by the Image class
        If lImageHasBeenPreserved Then
        Else

            ' If we cannot save the image
            If Not SaveAsHighQualityJpegFile() Then

            End If

        End If

        ' Remove this object from memory
        loImage.Dispose()

        ' Reset the values
        cFile = ""
        cFileDestination = ""
        lResizeButNoCrop = False

        Return True
    End Function

    ' Save an image into a JPG format
    Public Function SaveAsHighQualityJpegFile() As Boolean
        Dim loEncoderParameters As System.Drawing.Imaging.EncoderParameters = Nothing
        Dim loImageCodecInfo As System.Drawing.Imaging.ImageCodecInfo = Nothing

        ' Set Image codec of JPEG type, the index of JPEG codec is "1"       
        loImageCodecInfo = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()(1)

        ' Set the parameters for defining the quality of the thumbnail... here it is set to 100%
        loEncoderParameters = New System.Drawing.Imaging.EncoderParameters(1)

        loEncoderParameters.Param(0) = New System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 95)

        oImage.Save(cFileDestination, loImageCodecInfo, loEncoderParameters)

        Return True
    End Function

Anyone can confirm in there something that would be related to OS specific?