This class extracts all images from a PDF file and save them in JPEG format using PDFBOX 1.8.8

ImageExtractor.java

package com.kbashar.pdfboxtryout;

import org.apache.pdfbox.cos.COSBase;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDJpeg;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDPixelMap;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObject;
import org.apache.pdfbox.pdmodel.graphics.xobject.PDXObjectImage;

import javax.imageio.ImageIO;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Created by kbashar on 2/24/15.
 */

/**
 * This class extracts all images from a PDF file and save them in JPEG format using PDFBOX 1.8.8
 */

public class ImageExtractor {
    public static void main(String[] args) throws IOException {
        PDDocument document = null;
        if (args.length!=1) {
            System.out.println("Please provide a PDF file name");
            return;
        }
        try {
            document = PDDocument.load(args[0]);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }
        //get all pages from a PDF document
        List<PDPage> pages = document.getDocumentCatalog().getAllPages();
        int pageCount = 0;
        for (PDPage page:pages) {
            pageCount++;
            Map<String, PDXObject> xobj = null;

            //get the XObject from a page's resource dictionary
            xobj = page.getResources().getXObjects();
            int imageCount =0;
            for (Map.Entry<String,PDXObject> entry:xobj.entrySet()) {
                PDXObject obj = entry.getValue();

                //XObject can be of various type like image, form. But we here only need Images.

                if (obj instanceof PDXObjectImage)  {
                    imageCount++;
                    String imageName = "page_"+pageCount+"image_"+imageCount+".jpeg";
                    PDXObjectImage image = (PDXObjectImage) obj;
                    // this method might throw an exception javax.imageio.IIOException in OPEN JDK
                    ImageIO.write(
                            image.getRGBImage(),
                            "JPEG",
                            new FileOutputStream(imageName)
                    );
                }
            }
        }

}
}

How to extract images in the proper order (left-to-right, top-to-bottom)?