Merge N PDFs and Add Outline/Bookmarks with Custom Title

[Resurg3nt]

I run pdf-lib in a node.js environment, together with minimist to pass arguments.

I pass a series of files to merge in using an --a parameter, and the corresponding bookmark/outline name for the first page of each of the PDFs that are being combined into the merged PDF, under the --ab parameter.

So I would call the pdf-lib from the command line as follows:-

node main.js --a 1.pdf --a 2.pdf --a 3.pdf --a 4.pdf --ab "Document 1" --ab "Document 2" --ab "Document 3" --ab "Document 4"

I have tried creating the outlines/bookmarks using the following code, but all that happens is that two outlines/bookmarks are added and they both are named Document 1. Can you let me know where I have gone wrong?

I took this code from a comment in Issue #127.

const { PDFDocument, PDFPageLeaf, PDFDict, PDFString, PDFArray, PDFName, PDFNull, PDFNumber, StandardFonts, rgb } = require('pdf-lib');
const fs = require('fs');
const parameters = require('minimist')(process.argv.slice(2));

var mergeFiles = parameters["a"];
var mergeFLength = mergeFiles.length;
var bookMarkDescs = parameters["ab"];
var buffers = [];
var bookmarkPages = [];
var outlineItemArr = [];
var outlineItemRefsArr = [];
var pageCount = 0;

const getPageRefs = (pdfDoc) => {
    const refs = [];
    pdfDoc.catalog.Pages().traverse((kid, ref) => {
    if (kid instanceof PDFPageLeaf) refs.push(ref);
    });
    return refs;
};

const createOutlineItem = (pdfDoc, title, parent, nextOrPrev, page, isLast = false) => {
    let array = PDFArray.withContext(pdfDoc.context);
    array.push(page);
    array.push(PDFName.of("XYZ"));
    array.push(PDFNull);
    array.push(PDFNull);
    array.push(PDFNull);
    const map = new Map();
    map.set(PDFName.Title, PDFString.of(title));
    map.set(PDFName.Parent, parent);
    map.set(PDFName.of(isLast ? "Prev" : "Next"), nextOrPrev);
    map.set(PDFName.of("Dest"), array);

    return PDFDict.fromMapWithContext(map, pdfDoc.context);
}

for (var i = 0; i < mergeFLength; i++){	
	var fileBuffer = fs.readFileSync(mergeFiles[i]);
	buffers.push(fileBuffer);
}

if(buffers.length != 0){
	var output_file = mergePDFDocuments(buffers);
}

async function mergePDFDocuments(documents) {
	const mergedPdf = await PDFDocument.create();

	for (let document of documents) {
		document = await PDFDocument.load(document);
		if(bookmarkPages.length == 0){
			bookmarkPages.push(0);
			pageCount = pageCount + document.getPageCount();
			bookmarkPages.push(pageCount);			
		} else {
			pageCount = pageCount + document.getPageCount();
			bookmarkPages.push(pageCount);
		}
		const copiedPages = await mergedPdf.copyPages(document, document.getPageIndices());
		copiedPages.forEach((page) => mergedPdf.addPage(page));    
	}
	bookmarkPages.pop();
	
	var references = getPageRefs(mergedPdf);	
	
	const outlinesDictRef = mergedPdf.context.nextRef(); 
	
	for (var y = 0; y < bookmarkPages.length; y++){	
		var pdf_reference = references[bookmarkPages[y]];
		var bookmark_title = bookMarkDescs[y];
		var outlineItemRef = mergedPdf.context.nextRef();
		outlineItemRefsArr.push(outlineItemRef);
		if(bookmarkPages[bookmarkPages.length - 1] === bookmarkPages[y]){
			console.log("last value");
			var outlineItem_last = createOutlineItem(mergedPdf, bookmark_title, outlinesDictRef, outlineItemRef, pdf_reference, true);	
			outlineItemArr.push(outlineItem_last);			
		} else {
			var outlineItem = createOutlineItem(mergedPdf, bookmark_title, outlinesDictRef, outlineItemRef, pdf_reference);		
			outlineItemArr.push(outlineItem);
		}
	}
	
	var outlinesDictMap = new Map();
	var countOfBookmarks = outlineItemArr.length;
	var firstBookmark = outlineItemArr[0];
	var lastBookmark = outlineItemArr[countOfBookmarks-1];
	
	outlinesDictMap.set(PDFName.Type, PDFName.of("Outlines"));
	outlinesDictMap.set(PDFName.of("First"), firstBookmark);
	outlinesDictMap.set(PDFName.of("Last"), lastBookmark);
	outlinesDictMap.set(PDFName.of("Count"), PDFNumber.of(countOfBookmarks));	
	
	for (var z = 0; z < bookmarkPages.length; z++){	
		mergedPdf.context.assign(outlineItemRefsArr[z], outlineItemArr[z]);
	}		
	
	console.log(outlinesDictMap);
	
	mergedPdf.catalog.set(PDFName.of("Outlines"),outlinesDictRef);
	
	const outlinesDict = PDFDict.fromMapWithContext(outlinesDictMap, mergedPdf.context);

	mergedPdf.context.assign(outlinesDictRef, outlinesDict);	

	fs.writeFileSync('output_merge.pdf', await mergedPdf.save());
}

[Hopding]

Added this to the roadmap for tracking: #998.