OBVIUS (Object-Based Vision and Image Understanding System) is an image-processing system based on Common Lisp and CLOS (Common Lisp Object System). The system provides a flexible interactive user interface for working with images, image-sequences, and other pictorially displayable objects. By using Lisp as its primary language, the system is able to take advantage of the interpretive lisp environment (the ``listener''), object-oriented programming, and the extensibility provided by incremental compilation. The top-level of OBVIUS is implemented in Common Lisp, thus providing an interpreted, object-oriented programming environment. The low-level floating point operations are implemented in C for efficiency. A graphical user interface, based on menus and dialog boxes is also provided, in addition to the Lisp interpreter (listener). In the typical mode of interaction, the user types an expression to the lisp listener (or enters a command in a dialog box) and it returns a result. A picture of that result will then be automatically displayed in a window. Each window contains a circular stack of pictures. The user can cycle through this stack using mouse clicks with certain shift (``bucky'') key combinations. Commonly used operations such as histogram and zoom are also provided via mouse clicks. The system provides a library of low-level image processing routines. Some examples of these are - arithmetic operations (add, multiply, lookup-table point operations, etc) - image statistics (mean, variance, kurtosis, maximum, histograms etc) - convolutions, Fourier transforms, Hilbert transforms - geometric operations (crop, slice, rotate, flip-x, etc) - comparisons (greater-than, etc) - synthetic image generation - matrix operations OBVIUS also provides postscript output of pictures. Writing new operations in OBVIUS is relatively simple, and it is straightforward to add new viewable and picture types. OBVIUS currently runs on Sun and SGI workstations in Lucid v4.1 Common Lisp. For the Sun implementation, it also requires the LispView interface to OpenWindows/X, which is available free of charge on the X11 distribution tape. LispView is also available in the ftp directory on white.stanford.edu. OBVIUS is available via anonymous ftp from white.stanford.edu, IP number 36.121.0.16. Documentation (latex), and a User's Guide with installation instructions are included in the tarfile. Since it is currently an in-house product it comes without warrantee or support. For more information contact: David Heeger heeger@white.stanford.edu (415) 723-4048 Eero Simoncelli eero@central.cis.upenn.edu (215) 898-0376 Let us know if you get a copy of OBVIUS at your site so that we can keep a list of everybody (to send out bug fixes, inform you of new releases, etc.)