pnmhistmap: 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/pnmhistmap - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pnmhistmap - from package: netpbm

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

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