itself is a document preparation package overlaid on the typesetting package. While it is possible to produce diagrams and pictures of acceptable appearance using alone, the basic picture environment is difficult to learn, limited in scope, long-winded and, in general, extremely counter-intuitive. Its use is not recommended, except perhaps for very simple `boxes-and-lines' drawings.
In principle, however, the PostScript page description language used to drive output devices is capable of individually controlling every single possible pixel which might appear on a printed page (a page of 300dpi A4 LaserWriter output is made up of about 8000000 pixels). Hence, any sufficiently well-behaved PostScript `program' can be added to output in such a way as to make the added text part of the document. All that is required is to tell where on the page the extra PostScript text will draw whatever it is to draw and how large a box should be left to draw it, and can be persuaded to fit the rest of the document around it. Graphics production methods used alongside are then directed to generate drawings starting at the PostScript `origin' page position, and when incorporated in the document appear at whatever `current point' the source specifies.
Several methods of generating graphics are available locally for users:
handles picture output for itself entirely internally, and its use will be discussed no further here; consult [Lamport86] for more details. The bulk of the remainder of this section concerns itself with `hints and tips' for getting around some of the more common problems associated with the other methods mentioned above.