persistence.cpp:2197:ann.xml(1): There should be space between attributes in function icvXMLParseTag

August 3, 2016
作者：dengshuai_super
出处：http://blog.youkuaiyun.com/dengshuai_super/article/details/52069634
声明：转载请注明作者及出处。

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注意⚠️：此问题还不算解决，只是暂时用了别人的库，以后解决了，会回来记录。因为我是做笔记，所以建议大家直接看文章最后。
Opencv3.1.0 , Ubuntu16.04 ,开发板Microzed和Zedboard都试过了，出现同样问题。

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charVec size:101
file /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp, line 2197 terminate called after throwing an instance of 'cv::Exception' 
what():/home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp:2197:error:(-212) /mnt/PRTest/resources/model/ann.xml(1):
There should be space between attributes in function icvXMLParseTag

http://www.th7.cn/Program/cp/201605/851893.shtml

/** @brief Loads algorithm from the file

     @param filename Name of the file to read.
     @param objname The optional name of the node to read (if empty, the first top-level node will be used)

     This is static template method of Algorithm. It's usage is following (in the case of SVM):
     @code
     Ptr<SVM> svm = Algorithm::load<SVM>("my_svm_model.xml");
     @endcode
     In order to make this method work, the derived class must overwrite Algorithm::read(const
     FileNode& fn).
*/

    template<typename _Tp> static Ptr<_Tp> load(const String& filename, const String& objname=String())
    {
        FileStorage fs(filename, FileStorage::READ);
        FileNode fn = objname.empty() ? fs.getFirstTopLevelNode() : fs[objname];
        Ptr<_Tp> obj = _Tp::create();
        obj->read(fn);
        return !obj->empty() ? obj : Ptr<_Tp>();
    }

  /** @brief Reads algorithm parameters from a file storage
    */
    virtual void read(const FileNode& fn) { (void)fn; }

    /** @brief Reads algorithm from the file node

     This is static template method of Algorithm. It's usage is following (in the case of SVM):
     @code
     Ptr<SVM> svm = Algorithm::read<SVM>(fn);
     @endcode
     In order to make this method work, the derived class must overwrite Algorithm::read(const
     FileNode& fn) and also have static create() method without parameters
     (or with all the optional parameters)
     */
    template<typename _Tp> static Ptr<_Tp> read(const FileNode& fn)
    {
        Ptr<_Tp> obj = _Tp::create();
        obj->read(fn);
        return !obj->empty() ? obj : Ptr<_Tp>();
    }

http://stackoverflow.com/questions/25831111/opencv-traincascade-build-intermediate-result/26301531#26301531

猜测一：xml本身出现了错误

Ubuntu 里面：/home/ds/桌面/EasyPR-master/resources/model/ann.xml

<?xml version="1.0"?>
<!opencv_storage>
<opencv_ml_ann_mlp>
  <format>3</format>
  <layer_sizes>120 40 65</layer_sizes>
  <activation_function>SIGMOID_SYM</activation_function>
  <f_param1>1.</f_param1>
  <f_param2>1.</f_param2>

我故意把第二行加了一个”!”,Ubuntu里运行程序：出现：

OpenCV Error: Parsing error (resources/model/ann.xml(2):
file /home/ds/opencv-3.1.0/modules/core/src/persistence.cpp, 
 line 2249 terminate called after throwing an instance of 'cv::Exception'
  what():  /home/ds/opencv-3.1.0/modules/core/src/persistence.cpp:2249: 
  error: (-212) resources/model/ann.xml(2): 
  <opencv_storage> tag is missing in function icvXMLParse

在已经做好opencv移植的arm linux里面运行，出现：

OpenCV Error: Parsing error (resources/model/ann.xml(1): 
There should be space between attributes) in icvXMLParseTag, 
file /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp, line 2197 what():  
  /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp:2197: error: (-212) resources/model/ann.xml(1):
   There should be space between attributes in function icvXMLParseTag

然后我只把ann.xml 的第一行改为
<?xml version !="1.0"?>
在arm linux 报错和Ubuntu 上一样：

OpenCV Error: Parsing error (resources/model/ann.xml(1): Attribute name should be followed by '=') in icvXMLParseTag, 
file /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp, 
line 2149 terminate called after throwing an instance of 'cv::Exception' what():  
/home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp:2149: 
error: (-212) resources/model/ann.xml(1): Attribute name should be followed by '=' in function icvXMLParseTag

我把ann.xml 的第一行改为
<?xml version = "1.0" >
arm linux显示错误：

OpenCV Error: Parsing error (resources/model/ann.xml(1): 
There should be space between attributes) in icvXMLParseTag, 
file /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp, 
line 2197 terminate called after throwing an instance of 'cv::Exception' what():  /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp:2197: 
error: (-212) resources/model/ann.xml(1): 
There should be space between attributes in function icvXMLParseTag

结果arm上没检测出最右边？的问题，Ubuntu检测出来了。

于是我用opencv官方的例子人脸识别的那个（FaceDetection），在Ubuntu上可以顺利跑起来，移植到arm 上之后，出现了同样的问题：

WARNING: Could not load classifier cascade for nested objects OpenCV Error: 
There should be space between attributes) in icvXMLParseTag, 
file /home/ds/build/opencv3.1.0/modules/core/src/persistence.cpp, line 2197
terminate called after throwing an instance of 'cv::Exception'
    what():  /home/ds/build/opencv-3.1.0/modules/core/src/persistence.cpp:2197: error: (-212) haarcascade_frontalface_alt.xml(1): 
    There should be space between attributes in function icvXMLParseTag

Aborted

说明这是通性的问题，正确的在Ubuntu上可以用的xml，移植到开发板上的arm linux里面时，就会出现
There should be space between attributes in function icvXMLParseTag 的问题。

猜测二：是arm上解析出现问题

开始时我怀疑是缺少libxml2库的问题导致了解析失败：（其实后来发现opencv是用自己的解析函数来解析xml）
于是我用ldd命令看Ubuntu程序链接了哪些库：
其中发现了xml2

 ldd demo_linux_amd64 

打印出：

linux-vdso.so.1 =>  (0x00007ffdeb3b3000)
   `libopencv_world.so.3.1 => /usr/local/lib/libopencv_world.so.3.1 (0x00007f62e0ffe000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f62e0c61000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f62e0957000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f62e0741000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f62e0378000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f62e015d000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f62dff59000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f62dfd3c000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f62dfb33000)
    libpng12.so.0 => /lib/x86_64-linux-gnu/libpng12.so.0 (0x00007f62df90e000)`
    libgtk-3.so.0 => /usr/lib/x86_64-linux-gnu/libgtk-3.so.0 (0x00007f62defdf000)
    libgdk-3.so.0 => /usr/lib/x86_64-linux-gnu/libgdk-3.so.0 (0x00007f62ded03000)
    libcairo.so.2 => /usr/lib/x86_64-linux-gnu/libcairo.so.2 (0x00007f62de9ef000)
    libgdk_pixbuf-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgdk_pixbuf-2.0.so.0 (0x00007f62de7cd000)
    libgobject-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 (0x00007f62de579000)
    `libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f62de268000)`
    libavcodec-ffmpeg.so.56 => /usr/lib/x86_64-linux-gnu/libavcodec-ffmpeg.so.56 (0x00007f62dce3e000)
    libavformat-ffmpeg.so.56 => /usr/lib/x86_64-linux-gnu/libavformat-ffmpeg.so.56 (0x00007f62dca40000)
    libavutil-ffmpeg.so.54 => /usr/lib/x86_64-linux-gnu/libavutil-ffmpeg.so.54 (0x00007f62dc7d1000)
    libswscale-ffmpeg.so.3 => /usr/lib/x86_64-linux-gnu/libswscale-ffmpeg.so.3 (0x00007f62dc542000)
    `/lib64/ld-linux-x86-64.so.2 (0x0000561e16755000)`
    libgmodule-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgmodule-2.0.so.0 (0x00007f62dc33d000)
    libpangocairo-1.0.so.0 => /usr/lib/x86_64-linux-gnu/libpangocairo-1.0.so.0 (0x00007f62dc130000)
    libX11.so.6 => /usr/lib/x86_6