C#实现将批量图片转为PDF文件

public bool ConvertJPG2PDF(string jpgfilepath, string pdf)
{
            
            var document = new iTextSharp.text.Document(iTextSharp.text.PageSize.A4, 25, 25, 25, 25);
            using (var stream = new FileStream(pdf, FileMode.Create, FileAccess.Write, FileShare.None))
            {
 
                iTextSharp.text.pdf.PdfWriter.GetInstance(document, stream);
                document.Open();
                
                string[] allfs = Directory.GetFiles(jpgfilepath);
                for (int i = 0; i < allfs.Length; i++)
                {
                    string jpgfile = allfs[i].ToLower();
                    if (jpgfile.IndexOf(".jpg") == -1 && jpgfile.IndexOf(".jpeg")==-1){
                        continue;
                    }
                    using (var imageStream = new FileStream(jpgfile, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
                    {
                        var image = iTextSharp.text.Image.GetInstance(imageStream);
                        if (image.Height > iTextSharp.text.PageSize.A4.Height - 25)
                        {
                            image.ScaleToFit(iTextSharp.text.PageSize.A4.Width - 25, iTextSharp.text.PageSize.A4.Height - 25);
                        }
                        else if (image.Width > iTextSharp.text.PageSize.A4.Width - 25)
                        {
                            image.ScaleToFit(iTextSharp.text.PageSize.A4.Width - 25, iTextSharp.text.PageSize.A4.Height - 25);
                        }
                        image.Alignment = iTextSharp.text.Image.ALIGN_MIDDLE;
                        document.Add(image);
                        imageStream.Close();
                    }
                }
                document.Close();
                stream.Close();
                return File.Exists(pdf);
            }
}