@echo off
    setlocal enableextensions disabledelayedexpansion

    for /f "delims=" %%a in ('hostname') do set "host=%%a"

    >output.txt (
        for %%z in (*.jpg) do for /f "delims=" %%a in ('
            certutil -hashfile "%%z" MD5 ^| find /v ":"
        ') do echo %host%,,%%z,,%%a
    )