C# 一个把PDF页转换成Bitmap后保存到本地bmp图片的程序，执行多次后，写入速度变慢

csczh 2018-12-14 10:15:39

C#下调用Acrobat的组件，for循环一直从PDF文件中取出一页转换成Bitmap最后保存到本地图片。
刚开始能够保持每秒8到9张的速度，每张图片8M左右。保持到2000多张的时候，每秒大概只能保存1到2张。
内存关闭内存分页，只用物理内存，内存占用也一直保持在10%多。



          Acrobat.CAcroPDPage pdfPage = null;

            Acrobat.CAcroPoint pdfPoint = null;

            Acrobat.CAcroRect pdfRect = null;

            Acrobat.CAcroPDDoc doc = (Acrobat.CAcroPDDoc)Microsoft.VisualBasic.Interaction.CreateObject("AcroExch.PDDoc", "");



            Bitmap bitmap = null;

            for (curPDFIdx = 0; curPDFIdx < PD.PlateList.Count; ++curPDFIdx)

            {

                //取出当前页

                pdfPage = (Acrobat.CAcroPDPage)doc.AcquirePage(curPDFIdx - 1);



                //得到当前页的大小  

                pdfPoint = (Acrobat.CAcroPoint)pdfPage.GetSize();

                //生成一个页的裁剪区矩形对象  

                pdfRect = (Acrobat.CAcroRect)Microsoft.VisualBasic.Interaction.CreateObject("AcroExch.Rect", "");



                int pdfWidth = pdfPoint.x * pdfDPI / 72;//默认PDF的点是72DPI得到的。

                int pdfHeight = pdfPoint.y * pdfDPI / 72;



                //设置裁剪矩形的大小为当前页的大小  

                pdfRect.Left = 0;

                pdfRect.right = (short)(pdfWidth);

                pdfRect.Top = 0;

                pdfRect.bottom = (short)(pdfHeight);



                //将当前页的裁剪区的内容编成图片后复制到剪贴板中//耗时30多毫秒  

                pdfPage.CopyToClipboard(pdfRect, 0, 0, (short)(100 * pdfDPI / 72));  //100指100%



                try

                {

                    System.Windows.IDataObject clipboardData = System.Windows.Clipboard.GetDataObject();

                    //检查剪贴板中的对象是否是图片，如果是图片则将其保存为指定格式的图片文件  

                    if (clipboardData.GetDataPresent(System.Windows.DataFormats.Bitmap))

                    {//InteropBitmap转换成Drawing.bitmap

                        int stride = ((pdfWidth * 32 + 31) & ~31) >> 3;

                        byte[] byte_arr = new byte[(int)(pdfHeight * stride)];

                        InteropBitmap interopBitmap = (InteropBitmap)clipboardData.GetData(System.Windows.DataFormats.Bitmap);

                        interopBitmap.CopyPixels(byte_arr, stride, 0);

                        System.Drawing.Imaging.BitmapData bmpData;



                        //The Width and Height should be static don't bother depending on the InteropBitmap for them

                        bitmap = new System.Drawing.Bitmap(pdfWidth, pdfHeight, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

                        bmpData = bitmap.LockBits(new System.Drawing.Rectangle(new System.Drawing.Point(), bitmap.Size), System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format32bppRgb);

                        System.Runtime.InteropServices.Marshal.Copy(byte_arr, 0, bmpData.Scan0, byte_arr.Length);

                        bitmap.UnlockBits(bmpData);



                        bitmap.Save(@"D:\" + curPDFIdx.ToString() + ".bmp");//10毫秒

                        bitmap.Dispose();

                    }

                }

                catch (Exception ex)

                {

                    ShowError(ex.Message, "");

                    return;

                }

                Marshal.ReleaseComObject(pdfPage);

                Marshal.ReleaseComObject(pdfRect);

                Marshal.ReleaseComObject(pdfPoint);

            }

  Marshal.ReleaseComObject(doc);