This class is the starting-point if you want to generate graphs. It handles the various objects involved (e.g. axes, title, list of data-elements). It also provides the basic functions to add data-elements (using addData()), for automatic determination of min/max values for the axes, for data-handling and for the final generation of the graph. An instance of Image_Graph is the root for a tree of class-instances that will store data and settings, will provide methods for customizing the appearance of your graph and will finally create the output (graph on a canvas).