iTextSharp adding new instances of an existing pag

问题:

Let's say I have a three page PDF and all three of them have AcroFields. I need to be able to generate a new PDF with page 2 repeated N number of times. Each new instance of page 2 will need to have the field names modified to make them distinct from the other instances of page 2. Can someone who's solved this problem before provide a syntax example?

回答1:

This is explained in the MergeForms2 example. You should split your document into 3 documents each having one page. Use the renameFields() method to create variations of the second page.

Concatenating forms is done like this:

Document document = new Document();
PdfCopy copy = new PdfCopy(document, new FileOutputStream(dest));
copy.setMergeFields();
document.open();
List<PdfReader> readers = new ArrayList<PdfReader>();
for (int i = 0; i < 3; ) {
    PdfReader reader = new PdfReader(renameFields(src, ++i));
    readers.add(reader);
    copy.addDocument(reader);
}
document.close();
for (PdfReader reader : readers) {
    reader.close();
}

A common mistake is to forget the setMergeFields() method.

回答2:

This works but generates a large file. I guess it is because the image on page 2 is duplicated many times instead of being reused.

public static void ExpandRepeatingPages(string sourcePdfPath, string outputPdfPath)
{
    /* figure out how many pages we are working with */
    var transientPdfReader = new PdfReader(sourcePdfPath);
    var numberOfPages = transientPdfReader.NumberOfPages;
    transientPdfReader.Close();

    var outputFileStream = new FileStream(outputPdfPath, FileMode.Create);
    var pdfCopyFields = new PdfCopyFields(outputFileStream);

    foreach (var pageNumber in Enumerable.Range(1, numberOfPages))
    {
        var pdfBytes = ExtractPageToBytes(sourcePdfPath, pageNumber);
        var pdfReader = new PdfReader(pdfBytes);
        pdfCopyFields.AddDocument(pdfReader);
        pdfReader.Close();

        if (pageNumber == 2)
        {
            foreach (var extraPageNumber in Enumerable.Range(2, 200))
            {
                var extraPagePdfBytes = RenamePageFields(pdfBytes, extraPageNumber);
                pdfReader = new PdfReader(extraPagePdfBytes);
                pdfCopyFields.AddDocument(pdfReader);
                pdfReader.Close();
            }
        }
    }

    pdfCopyFields.Close();
}

public static byte[] ExtractPageToBytes(string sourcePdfPath, int pageNumber)
{
    using (var memoryStream = new MemoryStream())
    {
        var pageNumbers = new System.Collections.ArrayList { pageNumber };
        var pdfReader = new PdfReader(sourcePdfPath);
        var pdfCopyFields = new PdfCopyFields(memoryStream);

        pdfReader.SelectPages(pageNumbers);
        pdfCopyFields.AddDocument(pdfReader);
        pdfReader.RemoveUnusedObjects();
        pdfCopyFields.Close();
        pdfReader.Close();
        return memoryStream.ToArray();
    }
}

private static byte[] RenamePageFields(byte[] pdfBytes, int pageNumber)
{
    using (var memoryStream = new MemoryStream())
    {
        var pdfReader = new PdfReader(pdfBytes);
        var pdfStamper = new PdfStamper(pdfReader, memoryStream);
        var acroFields = pdfStamper.AcroFields;
        var fieldNames = acroFields.Fields.Keys.Cast<String>().ToList();

        foreach (var fieldName in fieldNames)
        {
            var newName = String.Format("{0}_{1}", fieldName, pageNumber);
            acroFields.RenameField(fieldName, newName);
        }

        pdfStamper.Close();
        pdfReader.Close();
        return memoryStream.ToArray();
    }
}