Xiaolin Wu's line algorithm: Difference between revisions

The program outputs a transparency mask in Portable Gray Map format. It draws lines normal to a tractrix. They trace out a catenary.

Here is a script to run the program and produce a PNG image.

<syntaxhighlight lang="sh">

#!/bin/sh

sbcl --script xiaolin_wu_line_algorithm.lisp > alpha.pgm

pamgradient black black darkblue darkblue 800 800 > bluegradient.pam

pamgradient red red magenta magenta 800 800 > redgradient.pam

pamcomp -alpha=alpha.pgm redgradient.pam bluegradient.pam | pamtopng > image.png

</syntaxhighlight>

{{out}}

[[File:Xiaolin wu line algorithm CommonLisp.png|thumb|none|alt=A catenary as the evolute of a tractrix. Reddish gradient on bluish gradient.]]