This function will return a truecolor GD-resource. The GD-resource will have the size you supplied when creating the Image_Graph-instance. If you need a palette GD-resource (e.g. for writing of GIF-images) please be sure to downsample the truecolor GD-resource returned by this function yourself. A truecolor-resource is needed for all alpha-channel-features etc. to receive best possible image-quality. It's possible to optionally give this function an already existing gd-resource. It will then be used for drawing. Please note that (at the moment) no solid standard background-fill will be done.