openslide-write-png: 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 CentOS possible default full paths are:

/usr/bin/openslide-write-png - from package: openslide-tools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/openslide-write-png - from package: openslide-tools

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

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