png2swf: command not found

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

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/png2swf - from package: swftools

You may install the required package with command apt-get install {package}

Error in other languages:
png2swf: bevel nie gevind nie
png2swf: comandă negăsită
png2swf: comando não encontrado
png2swf: commande introuvable
png2swf: command not found
png2swf: käsku ei ole
png2swf: không tìm thấy lệnh
png2swf: komanda nerasta
png2swf: Kommando nicht gefunden.
png2swf: kommandot finns inte
png2swf: komut yok
png2swf: nie znaleziono polecenia
png2swf: níor aimsíodh an t-ordú
png2swf: no se encontró la orden
png2swf: no s'ha trobat l'ordre
png2swf: opdracht niet gevonden
png2swf: parancs nem található
png2swf: perintah tidak ditemukan
png2swf: príkaz nenájdený
png2swf: příkaz nenalezen
png2swf: команда не найдена
png2swf: командата не е открита
png2swf: 命令找不到
png2swf: コマンドが見つかりません