Java使用icepdf将pdf文件按页转成图片

<dependency>
 <groupId>org.icepdf.os</groupId>
 <artifactId>icepdf-core</artifactId>
 <version>6.1.2</version> 
 <exclusions>
  <exclusion>
   <groupId>javax.media</groupId>
   <artifactId>jai-core</artifactId>
  </exclusion>
 </exclusions>
</dependency>

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageOutputStream;

import org.apache.commons.logging.LogFactory;
import org.icepdf.core.exceptions.PDFException;
import org.icepdf.core.exceptions.PDFSecurityException;
import org.icepdf.core.pobjects.Document;
import org.icepdf.core.pobjects.Page;
import org.icepdf.core.util.GraphicsRenderingHints;


public class test20160929 {
 public static final String FILETYPE_JPG = "jpg";

 /**
  * 
  * 将指定的pdf文件转换为指定路径的图片
  * 
  * @param filepath 原文件路径，例如d:/test/test.pdf
  * 
  * @param imagepath 图片生成路径，例如 d:/test/
  * 
  * @param zoom 缩略图显示倍数，1表示不缩放，0.3则缩小到30%
  * 
  */
 public static void tranfer(String filepath, String imagepath, float zoom) throws PDFException, PDFSecurityException, IOException {
  Document document = null;
  float rotation = 0f;
  document = new Document();
  document.setFile(filepath);
  int maxPages = document.getPageTree().getNumberOfPages();

  for (int i = 0; i < maxPages; i++) {
   BufferedImage img = (BufferedImage) document.getPageImage(i, GraphicsRenderingHints.SCREEN, Page.BOUNDARY_CROPBOX, rotation, zoom);
   Iterator iter = ImageIO.getImageWritersBySuffix(FILETYPE_JPG);
   ImageWriter writer = (ImageWriter) iter.next();
   File outFile = new File(imagepath + new File(filepath).getName() + "_" + new DecimalFormat("000").format(i) + "." + FILETYPE_JPG);
   FileOutputStream out = new FileOutputStream(outFile);
   ImageOutputStream outImage = ImageIO.createImageOutputStream(out);
   writer.setOutput(outImage);
   writer.write(new IIOImage(img, null, null));
  }
  System.out.println("转换完成");
 }

 public static void main(String[] args) throws PDFException, PDFSecurityException, IOException {
  tranfer("d:/test/test.pdf", "d:/test/", 1);
 }
}