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Image masks

This example was written in response to the question Click How to make an image a qualified mask candidate in itext?



    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:
package com.itextpdf.samples.sandbox.images;

import com.itextpdf.kernel.geom.PageSize;
import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Image;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

public class MakeJpgMask {
    public static final String DEST = "./target/sandbox/images/make_jpg_mask.pdf";

    public static final String IMAGE = "./src/main/resources/img/javaone2013.jpg";
    public static final String MASK = "./src/main/resources/img/berlin2013.jpg";

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

        new MakeJpgMask().manipulatePdf(DEST);

    protected void manipulatePdf(String dest) throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
        PageSize pageSize = PageSize.A4.rotate();
        Document doc = new Document(pdfDoc, pageSize);

        ImageData image = ImageDataFactory.create(IMAGE);
        ImageData mask = convertToBlackAndWhitePng(MASK);

        Image img = new Image(image);
        img.scaleAbsolute(pageSize.getWidth(), pageSize.getHeight());
        img.setFixedPosition(0, 0);


    private static ImageData convertToBlackAndWhitePng(String image) throws IOException {
        BufferedImage bi = File(image));
        BufferedImage newBi = new BufferedImage(bi.getWidth(), bi.getHeight(), BufferedImage.TYPE_USHORT_GRAY);
        newBi.getGraphics().drawImage(bi, 0, 0, null);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ImageIO.write(newBi, "png", baos);
        return ImageDataFactory.create(baos.toByteArray());


using System;
using System.Drawing;
using System.IO;
using iText.IO.Image;
using iText.Kernel.Geom;
using iText.Kernel.Pdf;
using iText.Layout;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using iText.Kernel.Pdf.Xobject;
using Image = iText.Layout.Element.Image;

namespace iText.Samples.Sandbox.Images
    public class MakeJpgMask
        public static readonly String DEST = "results/sandbox/images/make_jpg_mask.pdf";

        public static readonly String IMAGE = "../../../resources/img/javaone2013.jpg";
        public static readonly String MASK = "../../../resources/img/berlin2013.jpg";

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

            new MakeJpgMask().ManipulatePdf(DEST);

        protected void ManipulatePdf(String dest)
            PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
            PageSize pageSize = PageSize.A4.Rotate();
            Document doc = new Document(pdfDoc, pageSize);

            ImageData image = ImageDataFactory.Create(IMAGE);
            ImageData mask = ConvertToBlackAndWhitePng(MASK);

            /* For soft image masks grayscale 8 bit images are usually used. As described in
             * the ConvertToBlackAndWhitePng, for image masks actual image colorspace doesn't
             * matter, only image pixel values are important. Grayscale images are just
             * convenient for this purpose.
             * Here we adjust SMask image dictionary, in order to accommodate to the hacks
             * that we've performed in ConvertToBlackAndWhitePng method. There we've created
             * an image in indexed color space and by default C# will add transparency to the
             * image. Both these properties are forbidden for images that serve as masks.
             * That's why we explicitly override colorspace to /DeviceGray (which corresponds
             * to grayscale) and we just erase own transparency (/Mask) from the dictionary
             * of mask-image.
            PdfImageXObject imageXObject = new PdfImageXObject(image);
            PdfStream imageXObjectStream = imageXObject.GetPdfObject().GetAsStream(PdfName.SMask);
            imageXObjectStream.Put(PdfName.ColorSpace, PdfName.DeviceGray);

            // Remove a redundant submask

            Image img = new Image(imageXObject);
            img.ScaleAbsolute(pageSize.GetWidth(), pageSize.GetHeight());
            img.SetFixedPosition(0, 0);


        private static ImageData ConvertToBlackAndWhitePng(String image)
            FileStream fileStream = new FileStream(image, FileMode.Open);

            /* Image masks shall have either 8 bit or 1 bit color depth.
             * In this example we create a soft mask, for which 8 bit image is used.
             * For images used as masks, image color space is not relevant, only the
             * values of image pixels are important because they define transparency
             * level.
             * In C#, however, 8 bits per pixel (bpp) images are not well supported,
             * therefore we need to perform some tricks to convert RGB 24bpp image
             * to 8 bit image. We will manually set image pixel 8 bit values according
             * to original image RGB pixel values.
             * Note that even though we create image with indexed colorspace
             * (Format8bppIndexed), we don't care what are the actual colors in color
             * palette, because as mentioned, we don't care about color space for masks.
            Bitmap original = new Bitmap(fileStream);
            Bitmap result = new Bitmap(original.Width, original.Height, PixelFormat.Format8bppIndexed);

            BitmapData data = result.LockBits(new System.Drawing.Rectangle(0, 0, result.Width, result.Height),
                ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);
            byte[] bytes = new byte[data.Height * data.Stride];
            Marshal.Copy(data.Scan0, bytes, 0, bytes.Length);

            // Convert all pixels to grayscale
            for (int y = 0; y < original.Height; y++)
                for (int x = 0; x < original.Width; x++)
                    var c = original.GetPixel(x, y);
                    var rgb = (byte) ((c.R + c.G + c.B) / 3);
                    bytes[y * data.Stride + x] = rgb;

            Marshal.Copy(bytes, 0, data.Scan0, bytes.Length);

            using (var stream = new MemoryStream())
                result.Save(stream, ImageFormat.Png);
                return ImageDataFactory.Create(stream.ToArray());

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