Blender Image Channel Splitter
If you do not have enough RAM, Blender api version may be not usable for textures bigger than 3K.
It takes 10-50 seconds to process images and it may use a lot of RAM for the time period.
(After that it frees the RAM.)
2K textures uses ~1GB RAM
3K textures uses ~2.5GB RAM
and grows exponantial-ish-ly.
How to install Pillow to Blender?