asp.net "the object is currently in use elsewhere"

microsoft.public.dotnet.framework

7 Nov 2006 10:12 PM

boeledi

Dear All,

I would really appreciate if someone could help me.
I am developing an ASP.NET web site and I have to deal with images
upload.
When the user is selecting an image, I save it as such together with a
thumbnail version.
The following piece of code attempts to reduce the image size in order
to generate the thumbnail.
Everything seems to work fine with Internet Explorer 6 but, using
Firefox, I receive the following exception:
"The object is currently in use elsewhere" when trying to save the
bitmap in the MemoryStream.

I don't understand.

Many thanks in advance, for any help.

Didier

'*********************************************************************
    '
    ' pf_ModifyImage Method
    '
    ' Modifies the width or height of an image.
    '

'*********************************************************************
    Private Function pf_ModifyImage(ByVal original() As Byte, ByVal
width As Integer, ByVal height As Integer, ByVal contentType As String)
As Byte()

        ' original:    byte array of the image
        ' width:    new image width
        ' height:    new image height
        ' contentType:    type of image (this should be either pjpeg or
gif)

        ' convert byte array to image
        Dim stream As New MemoryStream(original)

        ' convert size to new dimensions
        Dim bmp As Bitmap = CType(Image.FromStream(stream), Bitmap)

        ' Calculate missing width or height
        If width = -1 Then
            width = Fix(System.Convert.ToDouble(height) /
System.Convert.ToDouble(bmp.Height) *
System.Convert.ToDouble(bmp.Width))
        End If
        If height = -1 Then
            height = Fix(System.Convert.ToDouble(width) /
System.Convert.ToDouble(bmp.Width) *
System.Convert.ToDouble(bmp.Height))
        End If

        Dim thumbBmp As New Bitmap(bmp, width, height)
        thumbBmp.Palette = pf_GetTransparentColorPalette(bmp)

        ' convert to stream in preparation to convert to byte array
        Dim stream2 As MemoryStream = New MemoryStream

        ' save the stream
        ' first we need to determine if image is JPG or GIF
        ' to determine the proper encoder type

        If contentType.ToLower().EndsWith("pjpeg") Then
                thumbBmp.Save(stream2, ImageFormat.Jpeg)
        Else
            thumbBmp.Save(stream2, ImageFormat.Gif)
'<<<<<<<<<<<<<<< Exception occurs here.
        End If

        ' cleanup
        thumbBmp.Dispose()
        bmp.Dispose()

        Return stream2.GetBuffer()
    End Function 'pf_ModifyImage

    Private Function pf_GetTransparentColorPalette(ByVal original As
Bitmap) As ColorPalette
        Dim testColor As Color
        Dim newColor As Color
        Dim pal As ColorPalette = original.Palette

        Dim i As Integer
        For i = 0 To (pal.Entries.Length - 1) - 1
            testColor = pal.Entries(i)

            If testColor.A = 0 Then
                newColor = Color.FromArgb(0, testColor)
                pal.Entries(i) = newColor
            End If
        Next i

        Return pal
    End Function 'pf_GetTransparentColorPalette