Replacing images

This is a code example of iText PDF, discover more.

31st May 2016
iText PDF

This example was written in response to the question How to convert colored images to black and white?

ReplaceImage.java
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/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2019 iText Group NV
    Authors: iText Software.
 
    For more information, please contact iText Software at this address:
    sales@itextpdf.com
 */
/**
 * This code sample was written by Bruno Lowagie in answer to this question:
 * http://stackoverflow.com/questions/26580912/pdf-convert-to-black-and-white-pngs
 */
package com.itextpdf.samples.sandbox.images;
 
import com.itextpdf.io.image.ImageDataFactory;
import com.itextpdf.kernel.pdf.*;
import com.itextpdf.kernel.pdf.xobject.PdfImageXObject;
import com.itextpdf.layout.element.Image;
import com.itextpdf.samples.GenericTest;
import com.itextpdf.test.annotations.type.SampleTest;
 
import org.junit.experimental.categories.Category;
 
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
 
@Category(SampleTest.class)
public class ReplaceImage extends GenericTest {
    public static final String DEST = "./target/test/resources/sandbox/images/replace_image.pdf";
    public static final String SRC = "./src/test/resources/pdfs/image.pdf";
 
    public static void main(String[] args) throws Exception {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        new ReplaceImage().manipulatePdf(DEST);
    }
 
    public static Image makeBlackAndWhitePng(PdfImageXObject image) throws IOException {
        BufferedImage bi = image.getBufferedImage();
        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 new Image(ImageDataFactory.create(baos.toByteArray()));
    }
 
    public static void replaceStream(PdfStream orig, PdfStream stream) throws IOException {
        orig.clear();
        orig.setData(stream.getBytes());
        for (PdfName name : stream.keySet()) {
            orig.put(name, stream.get(name));
        }
    }
 
    @Override
    protected void manipulatePdf(String dest) throws Exception {
        PdfDocument pdfDoc = new PdfDocument(new PdfReader(SRC), new PdfWriter(dest));
        PdfDictionary page = pdfDoc.getFirstPage().getPdfObject();
        PdfDictionary resources = page.getAsDictionary(PdfName.Resources);
        PdfDictionary xobjects = resources.getAsDictionary(PdfName.XObject);
        PdfName imgRef = xobjects.keySet().iterator().next();
        PdfStream stream = xobjects.getAsStream(imgRef);
        Image img = makeBlackAndWhitePng(new PdfImageXObject(stream));
        replaceStream(stream, img.getXObject().getPdfObject());
        pdfDoc.close();
    }
}

Click the following link to see the legacy example for iText 5. Except for security fixes, iText 5 is no longer being developed.



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