Why HttpPostedFile not reflecting image changes?

HttpPostedFile hpf = context.Request.Files[i] as HttpPostedFile;
Image img = Image.FromStream(hpf.InputStream);

                try
                {
                    foreach (var prop in img.PropertyItems)
                    {
                        if (prop.Id == 0x0112) //value of EXIF
                        {
                            var orientation = img.GetPropertyItem(prop.Id).Value[0];
                            switch (orientation)
                            {
                                case 1:
                                    // No rotation required.
                                    break;
                                case 2:
                                    img.RotateFlip(RotateFlipType.RotateNoneFlipX);                                    
                                    break;
                                case 3:
                                    img.RotateFlip(RotateFlipType.Rotate180FlipNone);                                    
                                    break;
			   }
                            // This EXIF data is now invalid and should be removed.
                            img.RemovePropertyItem(0x0112);
                        }
                    }                   
                    
                }
                catch (Exception ex)
                {
                    string error = ex.Message.ToString();
                }

string strImageName = System.Web.HttpContext.Current.Request.QueryString["ID"].ToString() + "-" + strPhotoCounter + ".jpg";

//----------------This block works-------------

Image img_converted = (Image)img.Clone();
               img_converted.Save(strOriginalPath + strImageName);
               img_converted.Dispose();
               img.Dispose();

//---------------- But this is not------------------
		hpf.SaveAs(strOriginalPath + strImageName);
                img.Dispose();

It work if it done "Clone" but not with "HttpPostedFile.SaveAs" why this is so??