ps2png: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ps2png - from package: tth-common

You may install the required package with command apt-get install {package}
Error in other languages:
ps2png: bevel nie gevind nie
ps2png: comandă negăsită
ps2png: comando não encontrado
ps2png: commande introuvable
ps2png: command not found
ps2png: käsku ei ole
ps2png: không tìm thấy lệnh
ps2png: komanda nerasta
ps2png: Kommando nicht gefunden.
ps2png: kommandot finns inte
ps2png: komut yok
ps2png: nie znaleziono polecenia
ps2png: níor aimsíodh an t-ordú
ps2png: no se encontró la orden
ps2png: no s'ha trobat l'ordre
ps2png: opdracht niet gevonden
ps2png: parancs nem található
ps2png: perintah tidak ditemukan
ps2png: príkaz nenájdený
ps2png: příkaz nenalezen
ps2png: команда не найдена
ps2png: командата не е открита
ps2png: 命令找不到
ps2png: コマンドが見つかりません