性能不佳使用ITextSharp将TIF转换为pdf [英] Bad performance convert tif to pdf using ITextSharp

问题描述

摘要:如何减少使用itextsharp将tif转换为pdf所需的时间?

Summary: How can I reduce the amount of time it takes to convert tifs to pdfs using itextsharp?

背景:我正在使用C#和itextsharp将一些相当大的tif转换为pdf，但性能却变得非常差.每个tif文件大约50kb，某些文档最多包含150个单独的tif文件(每个代表一页).对于一份132页的文档(约6500 kb)，转换大约需要13分钟.在转换过程中，其上运行的单个CPU服务器以100％的速度运行，这使我相信该进程受CPU限制.输出的pdf文件为3.5 MB.我可以接受这个大小，但是花费的时间对我来说似乎有点高.

Background: I'm converting some fairly large tif's to pdf using C# and itextsharp, and I am getting extremely bad performance. The tif files are approximately 50kb a piece, and some documents have up to 150 seperate tif files (each representing a page). For one 132 page document (~6500 kb) it took about 13 minutes to convert. During the conversion, the single CPU server it was running on was running at 100%, leading me to believe the process was CPU bound. The output pdf file was 3.5 MB. I'm ok with the size, but the time taken seem a bit high to me.

代码:

private void CombineAndConvertTif(IList<FileInfo> inputFiles, FileInfo outputFile)
{
    using (FileStream fs = new FileStream(outputFile.FullName, FileMode.Create, FileAccess.ReadWrite, FileShare.None))
    {
        Document document = new Document(PageSize.A4, 50, 50, 50, 50);
        PdfWriter writer = PdfWriter.GetInstance(document, fs);
        document.Open();
        PdfContentByte cb = writer.DirectContent;

        foreach (FileInfo inputFile in inputFiles)
        {
            using (Bitmap bm = new Bitmap(inputFile.FullName))
            {
                int total = bm.GetFrameCount(FrameDimension.Page);

                for (int k = 0; k < total; ++k)
                {
                    bm.SelectActiveFrame(FrameDimension.Page, k);
                    //Testing shows that this line takes the lion's share (80%) of the time involved.
                    iTextSharp.text.Image img =
                        iTextSharp.text.Image.GetInstance(bm, null, true);
                    img.ScalePercent(72f / 200f * 100);
                    img.SetAbsolutePosition(0, 0);

                    cb.AddImage(img);
                    document.NewPage();
                }
            }
        }

        document.Close();
        writer.Close();
    }

}

推荐答案

将GetInstance方法参数修改为

Modify GetInstance method argument to

GetInstance(bm, ImageFormat.Tiff) 

这可能会提高性能

iTextSharp.text.Image img =  iTextSharp.text.Image.GetInstance(bm, ImageFormat.Tiff);

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