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Replacing images

iText 5 is no longer being developed, except for security fixes. Click the following link to see an updated example for iText 7.

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

ReplaceImage.java
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/**
 * 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 sandbox.images;
 
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Image;
import com.itextpdf.text.pdf.PRStream;
import com.itextpdf.text.pdf.PdfDictionary;
import com.itextpdf.text.pdf.PdfImage;
import com.itextpdf.text.pdf.PdfName;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import com.itextpdf.text.pdf.PdfStream;
import com.itextpdf.text.pdf.parser.PdfImageObject;
 
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
 
import javax.imageio.ImageIO;
import sandbox.WrapToTest;
 
@WrapToTest
public class ReplaceImage {
    
    public static final String SRC = "resources/pdfs/image.pdf";
    public static final String DEST = "results/images/image_replaced.pdf";
 
    public static void main(String[] args) throws DocumentException, IOException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        new ReplaceImage().manipulatePdf(SRC, DEST);
    }
 
    public void manipulatePdf(String src, String dest) throws DocumentException, IOException {
        PdfReader reader = new PdfReader(src);
        PdfDictionary page = reader.getPageN(1);
        PdfDictionary resources = page.getAsDict(PdfName.RESOURCES);
        PdfDictionary xobjects = resources.getAsDict(PdfName.XOBJECT);
        PdfName imgRef = xobjects.getKeys().iterator().next();
        PRStream stream = (PRStream) xobjects.getAsStream(imgRef);
        Image img = makeBlackAndWhitePng(new PdfImageObject(stream));
        PdfImage image = new PdfImage(makeBlackAndWhitePng(new PdfImageObject(stream)), "", null);
        replaceStream(stream, image);
        PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
        stamper.close();
        reader.close();
    }
    
    public static Image makeBlackAndWhitePng(PdfImageObject image) throws IOException, DocumentException {
        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 Image.getInstance(baos.toByteArray());
    }
    
    public static void replaceStream(PRStream orig, PdfStream stream) throws IOException {
        orig.clear();
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        stream.writeContent(baos);
        orig.setData(baos.toByteArray(), false);
        for (PdfName name : stream.getKeys()) {
            orig.put(name, stream.get(name));
        }
    }
}


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