java使用renderer将pdf按页转换为图片

import java.awt.Image; import java.awt.Rectangle; import java.awt.image.BufferedImage; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.RandomAccessFile; import java.lang.reflect.Method; import java.nio.MappedByteBuffer; import java.nio.channels.FileChannel; import java.security.AccessController; import java.security.PrivilegedAction; //如果com.sun.image找不到，就是Eclipse默认把这些受访问限制的API设成了ERROR。只要把Windows-Preferences-Java-Complicer-Errors/Warnings里面的Deprecated and restricted API中的Forbidden references(access rules)选为Warning就可以编译通过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 pdfToImage {   public static void main(String[] args) { String instructiopath="E:/临时文件1.pdf"; String picturepath = "E:/临时文件1/"; changePdfToImg(instructiopath,picturepath); }    public static int changePdfToImg(String instructiopath,String picturepath) {     int countpage =0;     try {       //instructiopath ="D:/instructio/2015-05-16/Android 4编程入门经典.pdf"       //picturepath = "D:/instructio/picture/2015-05-16/";              File file = new File(instructiopath);       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);       //创建图片文件夹       File dirfile = new File(picturepath);         if(!dirfile.exists()){            dirfile.mkdirs();         }       //获得图片页数       countpage = pdffile.getNumPages();       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()));         int n = 2;         /** 图片清晰度（n>0且n<7）【pdf放大参数】 */         Image img = page.getImage(rect.width * n, rect.height * n,             rect, /** 放大pdf到n倍，创建图片。 */             null, /** null for the ImageObserver */             true, /** fill background with white */             true /** block until drawing is done */         );         BufferedImage tag = new BufferedImage(rect.width * n,             rect.height * n, BufferedImage.TYPE_INT_RGB);         tag.getGraphics().drawImage(img, 0, 0, rect.width * n,             rect.height * n, null);         /**          * File imgfile = new File("D://work//mybook//FilesNew//img//" +          * i + ".jpg"); if(imgfile.exists()){          * if(imgfile.createNewFile()) { System.out.println("创建图片："+          * "D://work//mybook//FilesNew//img//" + i + ".jpg"); } else {          * System.out.println("创建图片失败！"); } }          */         FileOutputStream out = new FileOutputStream(picturepath+"/" + i             + ".png");         /** 输出到文件流 */         JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);         JPEGEncodeParam param2 = encoder.getDefaultJPEGEncodeParam(tag);         param2.setQuality(1f, true);         /** 1f~0.01f是提高生成的图片质量 */         encoder.setJPEGEncodeParam(param2);         encoder.encode(tag);         /** JPEG编码 */         out.close();       }       channel.close();       raf.close();       /*unmap(buf);*/  //pdf转化成图片后，释放MappedByteBuffer资源。调用unmap(buf);无效。      /** 如果要在转图片之后删除pdf，就必须要这个关闭流和清空缓冲的方法 */     } catch (FileNotFoundException e) {       e.printStackTrace();     } catch (IOException e) {       e.printStackTrace();     }     return countpage;        }    @SuppressWarnings("unchecked")   public static void unmap(final Object buffer) {     AccessController.doPrivileged(new PrivilegedAction() {       public Object run() {         try {           Method getCleanerMethod = buffer.getClass().getMethod(               "cleaner", new Class[0]);           getCleanerMethod.setAccessible(true);           sun.misc.Cleaner cleaner = (sun.misc.Cleaner) getCleanerMethod               .invoke(buffer, new Object[0]);           cleaner.clean();         } catch (Exception e) {           e.printStackTrace();         }         return null;       }     });   } }

Method m = FileChannelImpl.class.getDeclaredMethod("unmap",    MappedByteBuffer.class);   m.setAccessible(true);   m.invoke(FileChannelImpl.class, buf);