java使用renderer将pdf按页转换为图片

项目中遇到了需要把用户上传的word，execl，ppt每页截图保存。需要先用到jacob把资源转换为pdf，在通过pdf-renderer把每页截图下来。

首先下载相关jar包：

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; 
      } 
    }); 
  } 
}

成功释放mappedbytebuffer资源

method m = filechannelimpl.class.getdeclaredmethod("unmap",
    mappedbytebuffer.class);
   m.setaccessible(true);
   m.invoke(filechannelimpl.class, buf);

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。