java如何将pdf转换成image

package pdf;  import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import java.util.Date; import java.util.List;  import javax.imageio.ImageIO;  import org.apache.pdfbox.pdmodel.PDDocument; import org.apache.pdfbox.pdmodel.PDPage;  public class PDFBox {      @SuppressWarnings("rawtypes")   public static void main(String[] args) throws IOException {     String p=System.getProperty("user.dir") + "/"+"zk.pdf";            PDDocument doc = PDDocument.load(p);     int pageCount = doc.getNumberOfPages();     System.out.println(pageCount);     Date start = new Date();     try {       List pages = doc.getDocumentCatalog().getAllPages();       for(int i=0;i<pages.size();i++){         PDPage page = (PDPage) pages.get(i);         @SuppressWarnings("unused")         int width = new Float(page.getTrimBox().getWidth()).intValue();         @SuppressWarnings("unused")         int height = new Float(page.getTrimBox().getHeight()).intValue();         BufferedImage image = page.convertToImage();         ImageIO.write(image, "jpg", new File("img" + File.separator + (i + 1) + ".jpg"));         System.out.println("image in the page -->"+(i+1));       }     } catch (Exception e) {       e.printStackTrace();     }finally{       if(doc != null){         doc.close();       }     }     Date end = new Date();     System.out.println(end.getTime()-start.getTime());     System.out.println("over");   }    } 

package pdf;  import java.awt.Image; import java.awt.Rectangle; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel;  import com.sun.image.codec.jpeg.JPEGCodec; import com.sun.image.codec.jpeg.JPEGEncodeParam; import com.sun.image.codec.jpeg.JPEGImageEncoder; import com.sun.pdfview.PDFFile; import com.sun.pdfview.PDFPage;  public class PDFRenderer {      public static void main(String[] args) throws IOException{     String pdfRealePath=System.getProperty("user.dir") + "/"+"zk.pdf";     File file = new File(pdfRealePath);     RandomAccessFile raf = new RandomAccessFile(file, "r");     FileChannel channel = raf.getChannel();     MappedByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY,         0, channel.size());     PDFFile pdffile = new PDFFile(buf);          for (int i = 1; i <= pdffile.getNumPages(); i++) {       PDFPage page = pdffile.getPage(i);       Rectangle rect = new Rectangle(0, 0, ((int) page.getBBox()           .getWidth()), ((int) page.getBBox().getHeight()));       Image img = page.getImage(rect.width, rect.height, rect, null,true,true);       BufferedImage tag = new BufferedImage(rect.width, rect.height,           BufferedImage.TYPE_INT_RGB);       tag.getGraphics().drawImage(img, 0, 0, rect.width, rect.height,null);              FileOutputStream out = new FileOutputStream("img" + File.separator + (i + 1) + ".jpg"); // 输出到文件流       JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);       JPEGEncodeParam param2 = encoder.getDefaultJPEGEncodeParam(tag);       param2.setQuality(1f, false);// 1f是提高生成的图片质量       encoder.setJPEGEncodeParam(param2);       encoder.encode(tag); // JPEG编码       out.close();       System.out.println("image in the page -->"+(i+1));     }   } }