imgcmp: 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/imgcmp - from package: jasper

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

On Debian possible default full paths are:

/usr/bin/imgcmp - from package: libjasper-runtime

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

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