Remove interpolation flag from images in a pdf file

2016_01_31-remove_interpolation.java

import com.itextpdf.text.pdf.*;
import com.itextpdf.text.pdf.parser.PdfImageObject;

import java.io.FileOutputStream;

/**
 * This remove the interpolation flag in images in a given PDF file using iText 5.
 * Requires: iText 5
 * 
 * For more info, see:
 * https://stackoverflow.com/questions/20011515/how-to-remove-anti-aliasing-in-pdf-images
 */
public class RemoveInterpolation {
    public static void main(String[] args) {
        try {
            // Open files.
            PdfReader reader = new PdfReader("input.pdf");
            PdfStamper stamper = new PdfStamper(reader, new FileOutputStream("output.pdf"));

            // Loop through all objects in the PDF looking for images.
            for (int i = 0; i <= reader.getXrefSize(); i++) {
                // Only look for non-null objects that are streams.
                PdfObject pdfObject = reader.getPdfObject(i);
                if (pdfObject == null || !pdfObject.isStream()) {
                    continue;
                }

                // Check if the stream, is an image.
                PRStream stream = (PRStream) pdfObject;
                PdfObject pdfsubtype = stream.get(PdfName.SUBTYPE);

                // If stream is an image, get its dictionary and remove the interpolate flag.
                if (pdfsubtype != null && pdfsubtype.toString().equals(PdfName.IMAGE.toString())) {
                    PdfImageObject imageObject = new PdfImageObject(stream);
                    PdfDictionary inDict = imageObject.getDictionary();
                    if (inDict != null) {
                        inDict.remove(PdfName.INTERPOLATE);
                    }
                }
            }

            // Close output and input files, then exit.
            stamper.close();
            reader.close();
        } catch(Exception e) {
            System.out.println("Unable to process file, exception: " + e);
        }
    }
}