Highlighting text

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.stamper;

import com.itextpdf.kernel.colors.ColorConstants;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfReader;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;

import java.io.File;

public class HighLightByAddingContent {
    public static final String DEST = "./target/sandbox/stamper/high_light_by_adding_content.pdf";
    public static final String SRC = "./src/main/resources/pdfs/hello.pdf";

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

        new HighLightByAddingContent().manipulatePdf(DEST);
    }

    protected void manipulatePdf(String dest) throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC), new PdfWriter(dest));

        // The content, placed on a content stream before, will be rendered before the other content
        // and, therefore, could be understood as a background (bottom "layer")
        PdfCanvas canvas = new PdfCanvas(pdfDoc.getFirstPage().newContentStreamBefore(),
                pdfDoc.getFirstPage().getResources(), pdfDoc);

        canvas
                .saveState()
                .setFillColor(ColorConstants.YELLOW)
                .rectangle(36, 786, 66, 16)
                .fill()
                .restoreState();

        pdfDoc.close();
    }
}

C#

using System;
using System.IO;
using iText.Kernel.Colors;
using iText.Kernel.Pdf;
using iText.Kernel.Pdf.Canvas;

namespace iText.Samples.Sandbox.Stamper 
{
    public class HighLightByAddingContent 
    {
        public static readonly String DEST = "results/sandbox/stamper/high_light_by_adding_content.pdf";
        public static readonly String SRC = "../../../resources/pdfs/hello.pdf";

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

        protected void ManipulatePdf(String dest) 
        {
            PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC), new PdfWriter(dest));
            
            // The content, placed on a content stream before, will be rendered before the other content
            // and, therefore, could be understood as a background (bottom "layer")
            PdfCanvas canvas = new PdfCanvas(pdfDoc.GetFirstPage().NewContentStreamBefore(),
                    pdfDoc.GetFirstPage().GetResources(), pdfDoc);
            
            canvas
                    .SaveState()
                    .SetFillColor(ColorConstants.YELLOW)
                    .Rectangle(36, 786, 66, 16).Fill()
                    .RestoreState();
            
            pdfDoc.Close();
        }
    }
}