Along with all the slick widget packages--[BLT], [ClassyTcl],
and so on--which build in canvas-oriented barcharting, there's
a dead-simple but too-little-known [pure Tcl] technique for
generating barcharts for Web applications.

[[Show picture of example output.  Show sample code.
Discuss axes and legends.  Explain alternatives for
generation of color image.  Refer to color codes.]]