Adding labels to PostScript figures

There seems to be much confusion among mathematicians about how to add labels, particularly ones produced by TEX, to illustrations in PostScript. The basic problem is that although PostScript is very capable of dealing with text, even with the CM fonts usually used by TEX, it does not have built into it any way to produce the formatting which is important---even crucial---to mathematical comprehension.

Here is a more concrete example of the problem. We start with a graph of the function y = x2 for x = -1 to x=1 (click here to see the actual PostScript image):

We want to add to this a few labels to produce (click here to see the actual PostScript image):

The point is that the labels ought to be in TEX, as they are here.

We shall offer three ways to solve this problem. They differ in their answer to the questions: Where does text end and graphics begin? To what extent should one expect to poke around inside a graphics file? How much work is a well designed label in a figure worth?

Written by Bill Casselman with help from David Austin and Joel Feldman.