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    copied!<p>Take a look at this code : </p> <pre><code>//! Struct for a 2d marker struct Marker2d{ double x; //!&lt; x coordinate of marker in calibration phantom double y; //!&lt; y coordinate of marker in calibration phantom int id; //!&lt; some unique id (used for sequence id as well as for assigned 3d id) int code; //!&lt; type of marker (small = 0, large = 1) float size; //!&lt; real size of marker in 2D image (in pixel) double distanceToNearest; //!&lt; distance to nearest other marker /** * Overloaded stream insertion operator. Abbreviation for the output of 2d marker. \param output_out A reference to an std::ostream instance indicating the output stream \param marker_in A constant Marker2d reference indicating the 2d marker that we want to output \return a std::ostream reference containing the new output data */ friend std::ostream &amp; operator&lt;&lt;(std::ostream &amp; output_out, const Marker2d &amp; marker_in) { return output_out&lt;&lt; std::fixed &lt;&lt; std::setprecision(15) &lt;&lt;marker_in.x&lt;&lt;"\t"&lt;&lt;marker_in.y&lt;&lt;"\t"&lt;&lt;marker_in.id&lt;&lt;"\t" &lt;&lt;marker_in.code&lt;&lt;"\t"&lt;&lt;marker_in.size&lt;&lt;"\t"&lt;&lt;marker_in.distanceToNearest; } /** * Overloaded stream extraction operator. \param s_in A reference to an std::istream instance indicating the input stream \param marker_out A Marker2d reference indicating the 2d marker that will have its data members populated \return a std::istream reference indicating the input stream */ friend std::istream&amp; operator&gt;&gt;(std::istream&amp; s_in, Marker2d &amp; marker_out) { s_in &gt;&gt; marker_out.x &gt;&gt; marker_out.y &gt;&gt; marker_out.id &gt;&gt; marker_out.code &gt;&gt; marker_out.size &gt;&gt; marker_out.distanceToNearest; return s_in; } }; </code></pre> <p>This is a simple struct with overloaded >> and &lt;&lt; operators. This allows you to output to a file like myOfstreamFile &lt;&lt; obj; And read the other way around.</p> <p>If you have say, a thousand of objects stored in a file you can simply put them in a container like this : </p> <pre><code>std::vector&lt;Marker2d&gt; myMarkers; std::ifstream f( fileName_in.c_str() ); if(!f) throw std::exception(std::string("AX.Algorithms.ComputeAssignmentsTest::getMarkersFromFile - Could not open file : " + fileName_in + " for reading!").c_str()); //cool one liner to read objects from file... std::copy(std::istream_iterator&lt;AX::Calibration::Marker2d&gt;(f), std::istream_iterator&lt;AX::Calibration::Marker2d&gt;(), std::back_inserter(myMarkers)); </code></pre> <p>Of course you could provide other forms of input and output e.g. save to .xml format and parse it as a dom tree etc. This is just a sample.</p> <p><strong>EDIT : This will work for relatively simple objects. Look at serialization if you need something more complex</strong></p>
 

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