从PDF文件中提取页码 [英] Extract page number from PDF file

问题描述

我有一个PDF文档，可能是通过从另一个PDF文档中提取少量页面而创建的。我想知道如何获取页码。由于起始页码为572，因此完整的PDF文档应为1.

I have a PDF document which might have been created by extracting few pages from another PDF document. I am wondering How do I get the page number. As the starting page number is 572, which for a complete PDF document should have been 1.

您认为将PDF转换为XMl会对此问题进行排序吗？

Do you think converting the PDF into an XMl will sort this issue?

推荐答案

最后用iText搞清楚了。如果没有Bovrosky的暗示，那是不可能的。非常感谢他。发布代码示例：

Finally figured it out using iText. Would not have been possible without Bovrosky's hint. Tons of thanks to him. Posting the code sample:

public void process(PdfReader reader) {
    PRIndirectReference obj = (PRIndirectReference) dict.get(com.itextpdf.text.pdf.PdfName.PAGELABELS);
    System.out.println(obj.getNumber());
    PdfObject ref = reader.getPdfObject(obj.getNumber());
    PdfArray array = (PdfArray)((PdfDictionary) ref).get(com.itextpdf.text.pdf.PdfName.NUMS);
    System.out.println("Start Page: " + resolvePdfIndirectReference(array, reader));
}

private static int resolvePdfIndirectReference(PdfObject obj, PdfReader reader) {
    if (obj instanceof PdfArray) {
        PdfDictionary subDict = null;
        PdfIndirectReference indRef = null;
        ListIterator < PdfObject > itr = ((PdfArray) obj).listIterator();
        while (itr.hasNext()) {
            PdfObject pdfObj = itr.next();
            if (pdfObj instanceof PdfIndirectReference)
                indRef = (PdfIndirectReference) pdfObj;
            if (pdfObj instanceof PdfDictionary) {
                subDict = (PdfDictionary) pdfObj;
                break;
            }
        }
        if (subDict != null) {
            return resolvePdfIndirectReference(subDict, reader);
        } else if (indRef != null)
            return resolvePdfIndirectReference(indRef, reader);
    } else if (obj instanceof PdfIndirectReference) {
        PdfObject ref = reader.getPdfObject(((PdfIndirectReference) obj).getNumber());
        return resolvePdfIndirectReference(ref, reader);
    } else if (obj instanceof PdfDictionary) {
        PdfNumber num = (PdfNumber)((PdfDictionary) obj).get(com.itextpdf.text.pdf.PdfName.ST);
        return num.intValue();
    }
    return 0;
}

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