The figures for the Clifford Paterson slides (Web version) were produced
as follows:

1. Some figure was copied into CorelDraw.
   For graphs, the most accurate way to do this was to convert them
   into bitmaps, and use the bitmaps as a background to trace over.
   Some graphs were scanned in from paper publications; some were
   loaded into Ghostview as postscript files and grabbed (either
   the PrtScr button on a PC, or a utility like xv on UNIX)
   The remaining figures and equations were left in PowerPoint.
2. The images were grabbed (as above) to give bitmap versions.
3. In a paint package, like Aldus Photostyler, examine the bitmap
   to see what colour the background turned out, and to convert to 
   a greyscale GIF.
4. The program giftool can be used to specify the background colour
   of a GIF, so that it looks transparent when loaded into Netscape.
   Giftool also interlaces the GIFs, so they display incrementally.
   The shell-script  prettify  does all this.