Image should be implemented by Object subtypes on behalf of
components which display image/pixmap information onscreen, and which provide information (other than just widget borders, etc.
) via that image content. For instance, icons, buttons with icons, toolbar elements, and image viewing panes typically should implement
Image.
Image primarily provides two types of information: coordinate information (useful for screen review mode
of screenreaders, and for use by onscreen magnifiers), and descriptive information. The descriptive information is provided for
alternative, text-only presentation of the most significant information present in the image.