FileStorage: add simplified API for bindings

at least it is possible to read/ write calibration files. Updates #4282.

Also add CPP method for writing comments.

modules/core/include/opencv2/core/persistence.hpp

@@ -398,7 +398,7 @@ class CV_EXPORTS_W FileStorage
     FileNode operator[](const String& nodename) const;
 
     /** @overload */
-    CV_WRAP FileNode operator[](const char* nodename) const;
+    CV_WRAP_AS(getFileNode) FileNode operator[](const char* nodename) const;
 
     /** @brief Returns the obsolete C FileStorage structure.
     @returns Pointer to the underlying C FileStorage structure
@@ -425,6 +425,38 @@ class CV_EXPORTS_W FileStorage
      */
     void writeObj( const String& name, const void* obj );
 
+    /**
+     * @brief Simplified writing API to use with bindings.
+     * @param name Name of the written object
+     * @param val Value of the written object
+     */
+    CV_WRAP void write(const String& name, double val);
+    /// @overload
+    CV_WRAP void write(const String& name, const String& val);
+    /// @overload
+    CV_WRAP void write(const String& name, InputArray val);
+
+    /**
+     * @brief Simplified reading API to use with bindings.
+     * @param name Name of the object
+     * @param val Value of the object
+     */
+    CV_WRAP_AS(readReal)   void read(const String& name, CV_OUT double& val);
+    /// @overload
+    CV_WRAP_AS(readString) void read(const String& name, CV_OUT String& val);
+    /// @overload
+    CV_WRAP_AS(readMat)    void read(const String& name, CV_OUT Mat& val);
+
+    /** @brief Writes a comment.
+
+    The function writes a comment into file storage. The comments are skipped when the storage is read.
+    @param comment The written comment, single-line or multi-line
+    @param append If true, the function tries to put the comment at the end of current line.
+    Else if the comment is multi-line, or if it does not fit at the end of the current
+    line, the comment starts a new line.
+     */
+    CV_WRAP void writeComment(const String& comment, bool append = false);
+
     /** @brief Returns the normalized object name for the specified name of a file.
     @param filename Name of a file
     @returns The normalized object name.

modules/core/src/persistence.cpp

@@ -5271,6 +5271,40 @@ void FileStorage::writeObj( const String& name, const void* obj )
     cvWrite( fs, name.size() > 0 ? name.c_str() : 0, obj );
 }
 
+void FileStorage::write( const String& name, double val )
+{
+    *this << name << val;
+}
+
+void FileStorage::write( const String& name, const String& val )
+{
+    *this << name << val;
+}
+
+void FileStorage::write( const String& name, InputArray val )
+{
+    *this << name << val.getMat();
+}
+
+void FileStorage::read( const String& name, double& val )
+{
+    (*this)[name] >> val;
+}
+
+void FileStorage::read( const String& name, String& val )
+{
+    (*this)[name] >> val;
+}
+
+void FileStorage::read( const String& name, Mat& val )
+{
+    (*this)[name] >> val;
+}
+
+void FileStorage::writeComment( const String& comment, bool append )
+{
+    cvWriteComment(fs, comment.c_str(), append ? 1 : 0);
+}
 
 FileNode FileStorage::operator[](const String& nodename) const
 {