convert Chinese Font using jpegdevice

Hi,
My company Pou Chen have purchased Aspose.Pdf Product Family version 10.5 and we got some problem with Chinese font conversion and I am asking the question for them. The code is as below. We convert a pdf to image using jpegdevice, but the Chinese encoding turns out to be random characters in the image. Is there a way to specify the encoding like for Aspose Txt so the jpegdevice can convert the Chinese font properly?

using (FileStream imageStream = new FileStream(@"C:\Debug\" + filename + ".jpg", FileMode.Create))
                {
                    // Create Resolution object
                    Resolution resolution = new Resolution(200);

                    // Create JPEG device with specified attributes (Width, Height, Resolution, Quality)
                    // where Quality [0-100], 100 is Maximum
                    JpegDevice jpegDevice = new JpegDevice(resolution, 100);
                    jpegDevice.RenderingOptions.BarcodeOptimization = true;
                    //jpegDevice.RenderingOptions.SystemFontsNativeRendering = false;
                    //Aspose.Pdf.LoadOptions option = new Aspose.Pdf.LoadOptions();
                   
                    // Convert a particular page and save the image to stream
                    jpegDevice.Process(pdfDocument.Pages[pageCount], imageStream);

                    // Close stream
                    imageStream.Close();
                }