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Adding backgrounds using page events

Examples written in answer to questions such as:


pagebackgrounds

JAVA

JAVA 
/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2023 Apryse Group NV
    Authors: Apryse Software.

    For more information, please contact iText Software at this address:
    sales@itextpdf.com
 */
package com.itextpdf.samples.sandbox.events;

import com.itextpdf.kernel.colors.ColorConstants;
import com.itextpdf.kernel.events.Event;
import com.itextpdf.kernel.events.IEventHandler;
import com.itextpdf.kernel.events.PdfDocumentEvent;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfPage;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.AreaBreak;
import com.itextpdf.layout.element.Paragraph;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class PageBackgrounds {
    public static final String DEST = "./target/sandbox/events/page_backgrounds.pdf";

    public static void main(String[] args) throws Exception {
        File file = new File(DEST);
        file.getParentFile().mkdirs();

        new PageBackgrounds().manipulatePdf(DEST);
    }

    protected void manipulatePdf(String dest) throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
        pdfDoc.addEventHandler(PdfDocumentEvent.START_PAGE, new PageBackgroundsEventHandler());
        Document doc = new Document(pdfDoc);

        doc.add(new Paragraph("Prime Numbers"));
        doc.add(new AreaBreak());
        doc.add(new Paragraph("An overview"));
        doc.add(new AreaBreak());
        for (int i = 2; i < 301; i++) {
            List<Integer> factors = getFactors(i);
            if (factors.size() == 1) {
                doc.add(new Paragraph("This is a prime number!"));
            }

            for (int factor : factors) {
                doc.add(new Paragraph("Factor: " + factor));
            }

            if (300 != i) {
                doc.add(new AreaBreak());
            }
        }

        doc.close();
    }

    private static List<Integer> getFactors(int n) {
        List<Integer> factors = new ArrayList<>();
        for (int i = 2; i <= n; i++) {
            while (n % i == 0) {
                factors.add(i);
                n /= i;
            }
        }

        return factors;
    }

    private static class PageBackgroundsEventHandler implements IEventHandler {
        @Override
        public void handleEvent(Event currentEvent) {
            PdfDocumentEvent docEvent = (PdfDocumentEvent) currentEvent;
            PdfPage page = docEvent.getPage();

            int pageNumber = docEvent.getDocument().getNumberOfPages();

            // Background color will be applied to the first page and all even pages
            if (pageNumber % 2 == 1 && pageNumber != 1) {
                return;
            }

            PdfCanvas canvas = new PdfCanvas(page);
            Rectangle rect = page.getPageSize();
            canvas
                    .saveState()
                    .setFillColor(pageNumber < 3 ? ColorConstants.BLUE : ColorConstants.LIGHT_GRAY)
                    .rectangle(rect)
                    .fillStroke()
                    .restoreState();
        }
    }
}

C#

C# 
using System;
using System.Collections.Generic;
using System.IO;
using iText.Kernel.Colors;
using iText.Kernel.Events;
using iText.Kernel.Geom;
using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas;
using iText.Layout;
using iText.Layout.Element;

namespace iText.Samples.Sandbox.Events
{
    public class PageBackgrounds
    {
        public static readonly String DEST = "results/sandbox/events/page_backgrounds.pdf";

        public static void Main(String[] args)
        {
            FileInfo file = new FileInfo(DEST);
            file.Directory.Create();

            new PageBackgrounds().ManipulatePdf(DEST);
        }

        protected void ManipulatePdf(String dest)
        {
            PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
            pdfDoc.AddEventHandler(PdfDocumentEvent.START_PAGE, new PageBackgroundsEventHandler());
            Document doc = new Document(pdfDoc);

            doc.Add(new Paragraph("Prime Numbers"));
            doc.Add(new AreaBreak());
            doc.Add(new Paragraph("An overview"));
            doc.Add(new AreaBreak());
            for (int i = 2; i < 301; i++)
            {
                List<int> factors = GetFactors(i);
                if (factors.Count == 1)
                {
                    doc.Add(new Paragraph("This is a prime number!"));
                }

                foreach (int factor in factors)
                {
                    doc.Add(new Paragraph("Factor: " + factor));
                }

                if (300 != i)
                {
                    doc.Add(new AreaBreak());
                }
            }

            doc.Close();
        }

        private static List<int> GetFactors(int n)
        {
            List<int> factors = new List<int>();
            for (int i = 2; i <= n; i++)
            {
                while (n % i == 0)
                {
                    factors.Add(i);
                    n /= i;
                }
            }

            return factors;
        }

        private class PageBackgroundsEventHandler : IEventHandler
        {
            public void HandleEvent(Event currentEvent)
            {
                PdfDocumentEvent docEvent = (PdfDocumentEvent) currentEvent;
                PdfPage page = docEvent.GetPage();

                int pageNumber = docEvent.GetDocument().GetNumberOfPages();

                // Background color will be applied to the first page and all even pages
                if (pageNumber % 2 == 1 && pageNumber != 1)
                {
                    return;
                }

                PdfCanvas canvas = new PdfCanvas(page);
                Rectangle rect = page.GetPageSize();
                canvas
                    .SaveState()
                    .SetFillColor(pageNumber < 3 ? ColorConstants.BLUE : ColorConstants.LIGHT_GRAY)
                    .Rectangle(rect)
                    .FillStroke()
                    .RestoreState();
            }
        }
    }
}



pageborder

JAVA

JAVA 
/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2023 Apryse Group NV
    Authors: Apryse Software.

    For more information, please contact iText Software at this address:
    sales@itextpdf.com
 */
package com.itextpdf.samples.sandbox.events;

import com.itextpdf.kernel.colors.ColorConstants;
import com.itextpdf.kernel.events.Event;
import com.itextpdf.kernel.events.IEventHandler;
import com.itextpdf.kernel.events.PdfDocumentEvent;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.AreaBreak;
import com.itextpdf.layout.element.Paragraph;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public class PageBorder {
    public static final String DEST = "./target/sandbox/events/page_border.pdf";

    public static void main(String[] args) throws Exception {
        File file = new File(DEST);
        file.getParentFile().mkdirs();

        new PageBorder().manipulatePdf(DEST);
    }

    protected void manipulatePdf(String dest) throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
        pdfDoc.addEventHandler(PdfDocumentEvent.START_PAGE, new PageBorderEventHandler());
        Document doc = new Document(pdfDoc);

        for (int i = 2; i < 301; i++) {
            List<Integer> factors = getFactors(i);
            if (factors.size() == 1) {
                doc.add(new Paragraph("This is a prime number!"));
            }

            for (int factor : factors) {
                doc.add(new Paragraph("Factor: " + factor));
            }

            if (300 != i) {
                doc.add(new AreaBreak());
            }
        }

        doc.close();
    }

    private static List<Integer> getFactors(int n) {
        List<Integer> factors = new ArrayList<>();
        for (int i = 2; i <= n; i++) {
            while (n % i == 0) {
                factors.add(i);
                n /= i;
            }
        }

        return factors;
    }


    private static class PageBorderEventHandler implements IEventHandler {
        @Override
        public void handleEvent(Event currentEvent) {
            PdfDocumentEvent docEvent = (PdfDocumentEvent) currentEvent;
            PdfCanvas canvas = new PdfCanvas(docEvent.getPage());
            Rectangle rect = docEvent.getPage().getPageSize();

            canvas
                    .setLineWidth(5)
                    .setStrokeColor(ColorConstants.RED)
                    .rectangle(rect)
                    .stroke();
        }
    }
}

C#

C# 
using System;
using System.Collections.Generic;
using System.IO;
using iText.Kernel.Colors;
using iText.Kernel.Events;
using iText.Kernel.Geom;
using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas;
using iText.Layout;
using iText.Layout.Element;

namespace iText.Samples.Sandbox.Events
{
    public class PageBorder
    {
        public static readonly String DEST = "results/sandbox/events/page_border.pdf";

        public static void Main(String[] args)
        {
            FileInfo file = new FileInfo(DEST);
            file.Directory.Create();

            new PageBorder().ManipulatePdf(DEST);
        }

        protected void ManipulatePdf(String dest)
        {
            PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
            pdfDoc.AddEventHandler(PdfDocumentEvent.START_PAGE, new PageBorderEventHandler());
            Document doc = new Document(pdfDoc);

            for (int i = 2; i < 301; i++)
            {
                IList<int> factors = GetFactors(i);
                if (factors.Count == 1)
                {
                    doc.Add(new Paragraph("This is a prime number!"));
                }

                foreach (int factor in factors)
                {
                    doc.Add(new Paragraph("Factor: " + factor));
                }

                if (300 != i)
                {
                    doc.Add(new AreaBreak());
                }
            }

            doc.Close();
        }

        private static IList<int> GetFactors(int n)
        {
            IList<int> factors = new List<int>();
            for (int i = 2; i <= n; i++)
            {
                while (n % i == 0)
                {
                    factors.Add(i);
                    n /= i;
                }
            }

            return factors;
        }

        private class PageBorderEventHandler : IEventHandler
        {
            public void HandleEvent(Event currentEvent)
            {
                PdfDocumentEvent docEvent = (PdfDocumentEvent) currentEvent;
                PdfCanvas canvas = new PdfCanvas(docEvent.GetPage());
                Rectangle rect = docEvent.GetPage().GetPageSize();

                canvas
                    .SetLineWidth(5)
                    .SetStrokeColor(ColorConstants.RED)
                    .Rectangle(rect)
                    .Stroke();
            }
        }
    }
}


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