Resize image on the fly make the image lose quality online but locally works nice

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Resize image on the fly make the image lose quality online but locally works nice

I wrote this handler to resize images on the fly:

Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest


        'Read in the image filename to create a thumbnail of
        Dim imageUrl As String = context.Request.QueryString("img")
        'Make sure that the image URL doesn't contain any /'s or \'s
        If imageUrl.IndexOf("/") >= 0 Or imageUrl.IndexOf("\") >= 0 Then


            'We found a / or \ 
            context.Response.End()
        End If
        'Get the image.
        Dim fullSizeImg As System.Drawing.Image
        'fullSizeImg = System.Drawing.Image.FromFile(Server.MapPath(imageUrl))
        fullSizeImg = System.Drawing.Image.FromFile(imageUrl)
        Dim smallImage As System.Drawing.Image
        'Resize the image
        smallImage = DynamicImage.Resize(fullSizeImg, 225, 225, True)
        'Set the ContentType to "image/jpg" and output the image's data
        context.Response.ContentType = "image/jpg"
        ' Create an Encoder object based on the GUID 
        ' for the Quality parameter category.   
        Dim myEncoder As System.Drawing.Imaging.Encoder = System.Drawing.Imaging.Encoder.Quality
        ' Create an EncoderParameters object. 
        ' An EncoderParameters object has an array of EncoderParameter
        ' objects. In this case, there is only one    
        ' EncoderParameter object in the array.   
        Dim myEncoderParameters As New EncoderParameters(1)
        Dim myEncoderParameter As New EncoderParameter(myEncoder, 100&)
        myEncoderParameters.Param(0) = myEncoderParameter
        Dim jgpEncoder As ImageCodecInfo = GetEncoder(ImageFormat.Jpeg)
        smallImage.Save(context.Response.OutputStream, jgpEncoder, myEncoderParameters)
        'Dispose/clean up...   
        smallImage.Dispose()
        fullSizeImg.Dispose()
    End Sub

My problem is that this code return a good quality image on my local server but when i put online the image lose quality.

I tested this code on 2 different servers one with IIS6 and another with IIS7 but the same low quality happen.

What may be the reason of this strange issue? in which direction should i think?