Normally, an application does not create an imageclass object. Instead, it
will use a subclass of imageclass.  Currently, there are four subclasses:
frameiclass, sysiclass, fillrectclass, and itexticlass.

frameiclass
    An embossed or recessed rectangular frame image, that renders itself
    using the proper DrawInfo pens.  This class is intelligent enough to
    bound or center its contents.

sysiclass
    The class of system images.  The class includes the images for the
    system and GadTools gadgets.

fillrectclass
    A class of rectangle images that have frame and patternfill support.

itexticlass
    A specialized image class used for rendering text.

For more information on these classes see the Boopsi Class Reference in
the Appendix B of this manual.  It describes all of the existing public
classes, their methods, and their attributes.

 The Gadgetclass Subclasses