PDF imposition in Java

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2023 by Apryse Software Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

import com.pdftron.pdf.*;
import com.pdftron.sdf.SDFDoc;

//-----------------------------------------------------------------------------------
// The sample illustrates how multiple pages can be combined/imposed 
// using PDFNet. Page imposition can be used to arrange/order pages 
// prior to printing or to assemble a 'master' page from several 'source' 
// pages. Using PDFNet API it is possible to write applications that can 
// re-order the pages such that they will display in the correct order 
// when the hard copy pages are compiled and folded correctly. 
//-----------------------------------------------------------------------------------
public class ImpositionTest {

    public static void main(String[] args) {
        PDFNet.initialize(PDFTronLicense.Key());

        // Relative path to the folder containing test files.
        String input_path = "../../TestFiles/";
        String output_path = "../../TestFiles/Output/";

        try {
            System.out.println("-------------------------------------------------");
            System.out.println("Opening the input pdf...");

            String filein = input_path + "newsletter.pdf";
            String fileout = output_path + "newsletter_booklet.pdf";

            PDFDoc in_doc = new PDFDoc(filein);
            in_doc.initSecurityHandler();

            // Create a list of pages to import from one PDF document to another.
            Page[] copy_pages = new Page[in_doc.getPageCount()];
            int j = 0;
            for (PageIterator itr = in_doc.getPageIterator(); itr.hasNext(); j++) {
                copy_pages[j] = itr.next();
            }

            PDFDoc new_doc = new PDFDoc();
            Page[] imported_pages = new_doc.importPages(copy_pages);

            // Paper dimension for A3 format in points. Because one inch has
            // 72 points, 11.69 inch 72 = 841.69 points
            Rect media_box = new Rect(0, 0, 1190.88, 841.69);
            double mid_point = media_box.getWidth() / 2;

            ElementBuilder builder = new ElementBuilder();
            ElementWriter writer = new ElementWriter();

            for (int i = 0; i < imported_pages.length; ++i) {
                // Create a blank new A3 page and place on it two pages from the input document.
                Page new_page = new_doc.pageCreate(media_box);
                writer.begin(new_page);

                // Place the first page
                Page src_page = imported_pages[i];
                Element element = builder.createForm(src_page);

                double sc_x = mid_point / src_page.getPageWidth();
                double sc_y = media_box.getHeight() / src_page.getPageHeight();
                double scale = sc_x < sc_y ? sc_x : sc_y; // min(sc_x, sc_y)
                element.getGState().setTransform(scale, 0, 0, scale, 0, 0);
                writer.writePlacedElement(element);

                // Place the second page
                ++i;
                if (i < imported_pages.length) {
                    src_page = imported_pages[i];
                    element = builder.createForm(src_page);
                    sc_x = mid_point / src_page.getPageWidth();
                    sc_y = media_box.getHeight() / src_page.getPageHeight();
                    scale = sc_x < sc_y ? sc_x : sc_y; // min(sc_x, sc_y)
                    element.getGState().setTransform(scale, 0, 0, scale, mid_point, 0);
                    writer.writePlacedElement(element);
                }

                writer.end();
                new_doc.pagePushBack(new_page);
            }

            new_doc.save(fileout, SDFDoc.SaveMode.LINEARIZED, null);
            // output PDF new_doc
            new_doc.close();
            in_doc.close();
            System.out.println("Done. Result saved in newsletter_booklet.pdf...");
        } catch (Exception e) {
            e.printStackTrace();
        }

        PDFNet.terminate();
    }
}