An image set is an object that identifies the location of an image. The image is typically a large image to be broken down into sub-images. The sub-images must all have the same size and be positioned side by side.
The following functions are available to create image set objects:
make-general-image-set
make-icon-resource-image-set
make-scaled-image-set
make-scaled-general-image-set
make-resource-image-set