Image size proble when create pdf using itextsharp dll

thanks in advance
i am  creating pdf using itextsharp dll, but image is not display a proper size in pdf.my code is below
//**************************************************************************************
  '*******************************set Images

        Dim gif As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(Server.MapPath("~/Images/Img1.jpg"))
        gif.ScaleToFit(334.0F, 265.0F)
        Dim gif1 As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(Server.MapPath("~/Images/Img2.jpg"))

        Dim gif2 As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(Server.MapPath("~/Images/Img3.jpg"))
        Dim gif3 As iTextSharp.text.Image = iTextSharp.text.Image.GetInstance(Server.MapPath("~/Images/Img4.jpg" ...