lilypond-snapshot ps2png

[D Josiah Boothby]

using pedro kroeger's lilypond-snapshot (2.3.24, i believe), i'm trying to 
output to .png, but am getting the following error:

$ lilypond-snapshot --png pnging.ly

Now processing `pnging.ly'
Parsing...
Interpreting music... [2]
Preprocessing graphical objects...
Calculating line breaks... [2]
Layout output to `pnging.tex'...Converting to `pnging.dvi'...
Converting to `pnging.ps'...
sh: line 1: ps2png: command not found

$

do i need to install another package to get ps2png, or do i need to 
download the source from somewhere? (the lazy debian user doesn't want do 
do that :)

josiah