Android 读取文件头判断文件类型

Posted 2022-11-08

private static String getImageType() 

    // File file = new File("C:/Users/Administrator/Desktop/111.png");
    // File file = new File("C:/Users/Administrator/Desktop/111.jpg");
    File file = new File("C:/Users/Administrator/Desktop/111.bmp");
    if (!file.exists()) 
      System.err.println("--- file not exists! ---");
      return null;
    

    byte[] png_type = new byte[]  (byte) 0x89, (byte) 0x50, (byte) 0x4E,
        (byte) 0x47, (byte) 0x0D, (byte) 0x0A, (byte) 0x1A,
        (byte) 0x0A, \\0 ;
    byte file_head[] = new byte[9];

    try 
      FileInputStream fis = new FileInputStream(file);
      fis.read(file_head, 0, 9);
     catch (Exception e) 
      e.printStackTrace();
      return null;
    

    file_head[8] = \\0;
    switch (file_head[0]) 
    case (byte) 0xff:
      if (file_head[1] == (byte) 0xd8)
        return "jpg";// jpeg
    case (byte) 0x42:
      if (file_head[1] == (byte) 0x4D)
        return "bmp";// bmp
    case (byte) 0x89:
      if (file_head[1] == png_type[1] && file_head[2] == png_type[2]
          && file_head[3] == png_type[3]
          && file_head[4] == png_type[4]
          && file_head[5] == png_type[5]
          && file_head[6] == png_type[6]
          && file_head[7] == png_type[7])
        return "png";// png
    

    return null;