把PDF InputStream转JPG图片 并输出byte[] 保存至blob pdf多页时纵向拼接

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>fontbox</artifactId>
    <version>2.0.9</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.pdfbox/pdfbox -->
<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.9</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-logging/commons-logging -->
<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.2</version>
</dependency>

public static byte[] useStream(InputStream is) throws Exception {
    try {
      PDDocument pdf = PDDocument.load(is);
      int actSize = pdf.getNumberOfPages();
      List<BufferedImage> piclist = new ArrayList<BufferedImage>();
      for (int i = 0; i < actSize; i++) {
        BufferedImage image = new PDFRenderer(pdf).renderImageWithDPI(i, 100,
                ImageType.RGB);
        piclist.add(image);
      }
      byte[] bytes = yPic(piclist);
      is.close();
      return bytes;
    } catch (IOException e) {
      e.printStackTrace();
    }
    return null;
  }


  /**
   * 将宽度相同的图片，竖向追加在一起 ##注意：宽度必须相同  多页时纵向拼接
   *
   * @param piclist 文件流数组
   */
  public static byte[] yPic(List<BufferedImage> piclist) {// 纵向处理图片
    if (piclist == null || piclist.size() <= 0) {
      System.out.println("图片数组为空!");
      return null;
    }
    try {
      int height = 0, // 总高度
              width = 0, // 总宽度
              _height = 0, // 临时的高度 , 或保存偏移高度
              __height = 0, // 临时的高度，主要保存每个高度
              picNum = piclist.size();// 图片的数量
      int[] heightArray = new int[picNum]; // 保存每个文件的高度
      BufferedImage buffer = null; // 保存图片流
      List<int[]> imgRGB = new ArrayList<int[]>(); // 保存所有的图片的RGB
      int[] _imgRGB; // 保存一张图片中的RGB数据
      for (int i = 0; i < picNum; i++) {
        buffer = piclist.get(i);
        heightArray[i] = _height = buffer.getHeight();// 图片高度
        if (i == 0) {
          width = buffer.getWidth();// 图片宽度
        }
        height += _height; // 获取总高度
        _imgRGB = new int[width * _height];// 从图片中读取RGB
        _imgRGB = buffer.getRGB(0, 0, width, _height, _imgRGB, 0, width);
        imgRGB.add(_imgRGB);
      }
      _height = 0; // 设置偏移高度为0
      // 生成新图片
      BufferedImage imageResult = new BufferedImage(width, height,
              BufferedImage.TYPE_INT_RGB);
      for (int i = 0; i < picNum; i++) {
        __height = heightArray[i];
        if (i != 0)
          _height += __height; // 计算偏移高度
        imageResult.setRGB(0, _height, width, __height, imgRGB.get(i), 0, width); // 写入流中
      }
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      boolean flag = ImageIO.write(imageResult, "jpg", out);
      byte[] b = out.toByteArray();
      File outFile = new File("H:\temp.jpg");
      ImageIO.write(imageResult, "jpg", outFile);// 写图片到本地
      return b;
    } catch (Exception e) {
      e.printStackTrace();
    }
    return null;
  }