[CentOS] LVM

I need to shrink /home(755G) to 150GB and use free space to add to the
existing /(50G).
#df -kh
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/vg_web-lv_root 50G  7.8G   40G  17% /
tmpfs                 7.8G  384K  7.8G   1% /dev/shm
/dev/sda2             485M   79M  381M  18% /boot
/dev/sda1             200M  256K  200M   1% /boot/efi
/dev/mapper/vg_web-lv_home755G  6.2G  711G   1% /home

Need to have the step, can this be done online or need to go offline
(umount) the file systems.

Thanks