pdf转图片，以及多张图片合并

引入控件 Aspose.Pdf.dll
传入pdf地址 path
 private void GetBinary(string path)
        {
            Document pdfDocument = new Document(path);
            StringBuilder sb = new StringBuilder();
            MemoryStream streamReport111 = new MemoryStream();

            int quality = 0;
            Aspose.Pdf.Devices.Resolution resolution = new Aspose.Pdf.Devices.Resolution(500);
            Aspose.Pdf.Devices.JpegDevice jpgDevice = new Aspose.Pdf.Devices.JpegDevice(resolution, quality);
            List<Bitmap> list_bitmap = new List<Bitmap>();

            for (int pageCount = 1; pageCount <= pdfDocument.Pages.Count && pageCount <= pdfDocument.Pages.Count; pageCount++)
            {
                using (MemoryStream streamReport = new MemoryStream())
                {
               
                    jpgDevice.Process(pdfDocument.Pages[pageCount], streamReport);
                    list_bitmap.Add(new Bitmap(streamReport));

                    streamReport.Flush();

                    streamReport.Close();
                }
            }

            pdfDocument.Dispose();
            Response.ContentType = "application/jpg";

            Response.BinaryWrite(CombinImage(list_bitmap));
        }

        这种合并方式为画布合并，如果图片太多，会导致内存不足的错误
        /// <summary> 
        /// 多张图片的合并(上下合并),可拓展为左右合并
        /// </summary>
        private byte[] CombinImage(List<Bitmap> list_bitmap)
        {
            var width = list_bitmap[0].Width;
            //var width = Math.Max(img1.Width, img2.Width);
            int height = 0;
            foreach (var item in list_bitmap)
            {
                height += item.Height;
            }
       
            // 初始化画布(最终的拼图画布)并设置宽高
            Bitmap bitMap = new Bitmap(width, height);
            // 初始化画板
            System.Drawing.Graphics g1 = System.Drawing.Graphics.FromImage(bitMap);
            // 将画布涂为白色(底部颜色可自行设置)
            g1.FillRectangle(Brushes.White, new System.Drawing.Rectangle(0, 0, width, height));
            int pointy = 0;
            for (int i = 0; i < list_bitmap.Count; i++)
            {

                if (i == 0)
                {
                    pointy = 0;
                    g1.DrawImage(new Bitmap(list_bitmap[i]), 0, pointy, list_bitmap[i].Width, list_bitmap[i].Height);
                }
                else
                {
                    pointy += list_bitmap[i - 1].Height;
                    g1.DrawImage(new Bitmap(list_bitmap[i]), 0, pointy + 10, list_bitmap[i].Width, list_bitmap[i].Height);
                }
            }

            Image img = bitMap;
            MemoryStream ms = new MemoryStream();
            img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            return ms.GetBuffer();

        }

       这种为流模式合并，可以解决内存问题
        /// <summary>
        /// 调用此函数后使此两种图片合并，类似相册，有个
        /// 背景图，中间贴自己的目标图片
        /// </summary>
        /// <param name="sourceImg">底层图片</param>
        /// <param name="destImg">上层图片</param>
        public static System.IO.MemoryStream CombinImage(System.IO.MemoryStream sourceImgStream, System.IO.MemoryStream destImgStream/*, int iSrcWidth, int iSrcHight, int iDstWidth, int iDstHight*/)
        {
            System.Drawing.Image imgBack = System.Drawing.Image.FromStream(sourceImgStream);     //底层图像 
            System.Drawing.Image img = System.Drawing.Image.FromStream(destImgStream);        //上层图像



            //从指定的System.Drawing.Image创建新的System.Drawing.Graphics       
            Graphics g = Graphics.FromImage(imgBack);

            g.DrawImage(imgBack, 0, 0, imgBack.Width, imgBack.Height);      // g.DrawImage(imgBack, 0, 0, 相框宽, 相框高);
            //g.FillRectangle(System.Drawing.Brushes.Black, 16, 16, (int)112 + 2, ((int)73 + 2));//相片四周刷一层黑色边框

            //g.DrawImage(img, 照片与相框的左边距, 照片与相框的上边距, 照片宽, 照片高);
            g.DrawImage(img, imgBack.Width - img.Width -100, 100, img.Width, img.Height);
            GC.Collect();

            //输出文件流
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            imgBack.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            imgBack.Dispose();

            return ms;
        }