为什么我的代码将文档旋转 180 度？

Question

I have written a C# code that merges two pdf files upon downloading together but it rotates some (not all) documents 180 degrees. I have attached the sample file that I am uploading.

Kindly, help me on this.

Sample file

try
    {
        string NewFileName = "InspectionReport" + DateTime.Now.ToString("ddMMMyyyy HHmmss").Replace(" ", "");
        destinationFile = HostingEnvironment.MapPath(@"/Downloads/CNGCertificates/" + NewFileName + ".pdf");

        int f = 0;

        PdfReader reader = new PdfReader(sourceFiles[f]);

        int n = reader.NumberOfPages;

        Document document = new Document(reader.GetPageSizeWithRotation(1));

        PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(destinationFile, FileMode.Create));

        document.Open();
        PdfContentByte cb = writer.DirectContent;
        PdfImportedPage page;
        int rotation;

        while (f < sourceFiles.Length)
        {
            int i = 0;
            while (i < n)
            {
                i++;
                document.SetPageSize(reader.GetPageSizeWithRotation(i));
                document.NewPage();
                page = writer.GetImportedPage(reader, i);
                rotation = reader.GetPageRotation(i);
                if (rotation == 90 || rotation == 270)
                {
                    cb.AddTemplate(page, 0, -1f, 1f, 0, 0, reader.GetPageSizeWithRotation(i).Height);
                }
                else
                {
                    cb.AddTemplate(page, 1f, 0, 0, 1f, 0, 0);
                }

            }
            f++;
            if (f < sourceFiles.Length)
            {
                reader = new PdfReader(sourceFiles[f]);

                n = reader.NumberOfPages;

            }
        }

        document.Close();
    }

Answer 1

You are handling rotation of 90 and 270 identically. Thus, if source pages with a rotation value of 90 are handled as you expect, source pages with a rotation value of 270 consequentially will end up upside down.

Thus, you have to handle 270 separately, using the affine transformation rotating the other way:

cb.AddTemplate(page, 0, 1f, -1f, 0, reader.GetPageSizeWithRotation(i).Width, 0);

Similarly you'll have to handle the 180 value separately, too, unless you want such pages to end up upside down:

cb.AddTemplate(page, -1f, 0, 0, -1f, reader.GetPageSizeWithRotation(i).Width, reader.GetPageSizeWithRotation(i).Height);

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That all being said, you actually shouldn't use a normal PdfWriter for merging at all, you should use PdfCopy . Using PdfCopy you don't have to deal with details like rotation anymore. Furthermore, annotations are copied along and not dropped as with PdfWriter . Look here for example. (If you use a 5.5.x version, you don't have to differentiate between the PdfCopy variants mentioned there anymore, you can use the plain PdfCopy for all use cases. If you use a 4.x version, though, you do have to pick appropriately.)