imresize: 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/imresize - from package: wcstools

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

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