Create a New custom COSBase objects with pdfbox?

问题

Can we Create a new custom PDFOperator (like PDFOperator{BDC}) and COSBase objects(like COSName{P} COSName{Prop1} (again Prop1 will reference one more obj)) ? And add these to the root structure of a pdf?

I have read some list of parser tokens from an existing pdf document. I wanted to tag the pdf. In that process I will first manipulate the list of tokens with newly created COSBase objects. At last I will add them to root tree structure. So here how can I create a COSBase objects. I am using the code to extract tokens from pdf is

old_document = PDDocument.load(new File(inputPdfFile));
List<Object> newTokens = new ArrayList<>();
for (PDPage page : old_document.getPages()) 
{
    PDFStreamParser parser = new PDFStreamParser(page);
    parser.parse();
    List<Object> tokens = parser.getTokens();
    for (Object token : tokens) {
        System.out.println(token);
        if (token instanceof Operator) {
            Operator op = (Operator) token;     
        }
}
newTokens.add(token);
}

PDStream newContents = new PDStream(document);
document.addPage(page);
OutputStream out = newContents.createOutputStream(COSName.FLATE_DECODE);
ContentStreamWriter writer = new ContentStreamWriter(out);
writer.writeTokens(newTokens);
out.close();
page.setContents(newContents);
document.save(outputPdfFile);
document.close();

Above code will create a new pdf with all formats and images. So In newTokens list contains all existing COSBase objects so I wanted to manipulate with some tagging COSBase objects and if I saved the new document then it should be tagged without taking care of any decode, encode, fonts and image handlings.

First Is this idea will work? If yes then help me with some code to create custom COSBase objects. I am very new to java.

回答1:

Based on your document format you can insert marked content.

//Below code is to add   "/p <<MCID 0>> /BDC"

newTokens.add(COSName.getPDFName("P"));
currentMarkedContentDictionary = new COSDictionary();
currentMarkedContentDictionary.setInt(COSName.MCID, mcid);
mcid++;
newTokens.add(currentMarkedContentDictionary);
newTokens.add(Operator.getOperator("BDC"));

// After adding mcid you have to append your existing tokens TJ , TD, Td, T* ....
newTokens.add(existing_token);
// Closed EMC
newTokens.add(Operator.getOperator("EMC"));
//Adding marked content to the root tree structure.
structureElement = new PDStructureElement(StandardStructureTypes.P, currentSection);
structureElement.setPage(page);
PDMarkedContent markedContent = new PDMarkedContent(COSName.P, currentMarkedContentDictionary);
structureElement.appendKid(markedContent);
currentSection.appendKid(structureElement);

Thanks to @Tilman Hausherr

来源：https://stackoverflow.com/questions/56231681/create-a-new-custom-cosbase-objects-with-pdfbox

标签

java

accessibility

pdfbox

tagging