is a file format developed for the MAME (Multiple Arcade Machine Emulator) project but has since been adopted by a wide variety of emulators, including those for the PS2. A PS2 CHD ROM is essentially a compressed version of the game data that maintains the integrity of the original disc while significantly reducing file size.
for %%i in (*.iso) do chdman createcd -i "%%i" -o "%%~ni.chd" Ps2 Chd Roms