将pdf格式的文件转换成图片

public class PdfToImage {

    private static String UPLOAD_DIR = "upload" + File.separator;
    
    /**
     * 获取上传的文件
     * @param uploadPath
     * @param file
     * @return
     */
    private static File getUploadCalendarFile(String uploadPath,MultipartFile file)
    {
        File path = new File(uploadPath);
        if(!path.exists())
             path.mkdirs();
          String fileName = file.getOriginalFilename();
            String ext = fileName.substring(fileName.lastIndexOf("."));
            String uploadfileName = UUID.randomUUID().toString();
            uploadfileName = uploadfileName.replace("-", "");
            uploadfileName = uploadfileName + ext;
            String pdfpath = uploadPath+uploadfileName;
            File convFile = new File( pdfpath);
            try {
                file.transferTo(convFile);
            } catch (IllegalStateException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return convFile;
    }
    /**
     * 
     * @param pdfPath：pdf的路径
     * @param filePath：存放图片的路径
     * @return
     */
    public static String getPdfToImagePath(HttpServletRequest request,MultipartFile mulfile) {
         try {
            ServletContext contx = request.getSession().getServletContext();
            String savePath = contx.getRealPath("/") + UPLOAD_DIR;
            File pdfPath = getUploadCalendarFile(savePath,mulfile);
            if(null != pdfPath && pdfPath.exists())
            {
                String pdfUploadName =  pdfPath.getName();
                pdfUploadName = pdfUploadName.substring(0,pdfUploadName.lastIndexOf("."));
                //如果图片存放的路径不存在，则创建
                 String imgPicPaths = savePath + File.separator + pdfUploadName;
                 File file = new File(imgPicPaths);
                 if(!file.exists())
                     file.mkdirs();
                  //将pdf 转换成多张图片,图片名称按数字进行保存
                    int iImageCount = convertPdfToImage(pdfPath,imgPicPaths);
                    //如果正确读取pdf,图片的个数根据pdf的页数来判断
                    if(iImageCount > 0)
                    {
                        //读取filePath,图片路径下的第一张图片
                        String firstImg = imgPicPaths + File.separator + "1.png";
                        File fileFirst=new File(firstImg); 
                        if(fileFirst.exists())
                        {
                            String outPath = savePath + File.separator + pdfUploadName  + ".png";
                            //将生成的多张图片合并
                            File oneImgPath = mergeImage(firstImg,iImageCount,imgPicPaths,outPath);
                            if(null != oneImgPath && oneImgPath.exists())
                            {
                                //将生成的图片进行大小限制：设定宽度最大为900
                                ImageFixSizeUtil.compressImage(outPath, outPath, CalendarImgSizeEnum.MAXLENGTH.getiValue());
                                return outPath;
                            }
                        }
                    }else
                    {
                        if(file.exists() && file.isDirectory())
                        {
                            //删除目录文件夹
                            FileUtils.deleteDirectory(file);
                            if(pdfPath.exists())
                                pdfPath.delete();
                        }
                    }
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        }
         return null;
    }

    /**
     * 读取pdf文件， 生成图片，然后将图片合并
     * 
     * @return
     */
    private static int convertPdfToImage(File pdfPath, String filePath) {
        
        RandomAccessFile raf;
        try {
            raf = new RandomAccessFile(pdfPath, "r");
            FileChannel channel = raf.getChannel();
            MappedByteBuffer buf = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
            PDFFile pdffile = new PDFFile(buf);
            int iImageNum = 0;
            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, // null
                        true, // fill background with white
                        true // block until drawing is done
                );
                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(filePath + File.separator  + i + ".png"); // 输出到文件流
                ImageIO.write(tag, "png", out);
                tag.flush();
                out.flush();
                out.close();
                iImageNum += 1;
            }
            channel.close();
            raf.close();
            unmap(buf);// 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
            //生成图片后，清除pdf文件
            if(pdfPath.exists())
                pdfPath.delete();
            return iImageNum;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(pdfPath.exists()){
                pdfPath.delete();
            }
        }
        return 0;
    }

    /**
     * 将生成的图片合并成一张图片
     * 
     * @param firstImg
     * @param iPageSize
     * @param imgPath
     * @param outPath
     * @throws IOException
     */
    private static File mergeImage(String firstImg, int iPageSize, String imgPath, String outPath) throws IOException {
        // 读取第一张图片
        File fileOne = new File(firstImg);
        BufferedImage ImageOne = ImageIO.read(fileOne);
        int width = ImageOne.getWidth();// 图片宽度
        int height = ImageOne.getHeight();// 图片高度
        int iYHeight = 0;
        // 从图片中读取RGB
        int[] ImageArrayOne = new int[width * height];
        ImageArrayOne = ImageOne.getRGB(0, 0, width, height, ImageArrayOne, 0, width);
        // 生成新图片
        BufferedImage ImageNew = new BufferedImage(width, height * iPageSize, BufferedImage.TYPE_INT_RGB);
        ImageNew.setRGB(0, 0, width, height, ImageArrayOne, 0, width);// 设置左半部分的RGB
        ImageOne.flush();
        
        for (int i = 2; i <= iPageSize; i++) {
            File fileTwo = new File(imgPath + File.separator + String.valueOf(i) + ".png");
            BufferedImage ImageTwo = ImageIO.read(fileTwo);
            int[] ImageArrayTwo = new int[width * height];
            ImageArrayTwo = ImageTwo.getRGB(0, 0, width, height, ImageArrayTwo, 0, width);
            ImageTwo.flush();
            iYHeight = (i - 1) * height;
            ImageNew.setRGB(0, iYHeight, width, height, ImageArrayTwo, 0, width);// 设置右半部分的RGB
        }
        ImageNew.flush();
        File outFile = new File(outPath);
        ImageIO.write(ImageNew, "png", outFile);// 写图片
        //清空文件夹中内容
        File file = new File(imgPath);
        //删除目录 
        FileUtils.deleteDirectory(file);
        return outFile;
    }


    /**
     * 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
     * 
     * @param buffer
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    private 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;
            }
        });
    }
}