ePub size reduction and PNG conversion

[lostinlodos]

I'm looking to figure out if there is a built in way, or some extension I can use.
I guess I'm trying to ultimately reduce file sizes

I know the polish option breaks down fonts but that's not all that useful for ePub as far as I know.
Looking to convert photos/images to grey scale and maybe turn them into PNG rather than GIF, JPG?
Any anything else I can do genericly to reduce file sizes.

There's an app on Google Play called eBook Optimizer from NATYGAMES that I've tried.
Surprised at the MASSIVE file size reduction it does but I'd hate to have to move files to my phone, run the app, then move them back to my computer to transfer to other devices.

Want to do whatever it does+ with Calibre.

[BetterRed]

Originally Posted by lostinlodos

I'm looking to figure out if there is a built in way, or some extension I can use.
I guess I'm trying to ultimately reduce file sizes

I know the polish option breaks down fonts but that's not all that useful for ePub as far as I know.
Looking to convert photos/images to grey scale and maybe turn them into PNG rather than GIF, JPG?
Any anything else I can do genericly to reduce file sizes.

There's an app on Google Play called eBook Optimizer from NATYGAMES that I've tried.
Surprised at the MASSIVE file size reduction it does but I'd hate to have to move files to my phone, run the app, then move them back to my computer to transfer to other devices.

Want to do whatever it does+ with Calibre.

If you were able to provide a couple of Before and After NatyGames samples then someone may be able to give you some tips.

You say you got MASSIVE savings, the site claims 5-15% reduction which I would have thought was modest.

BR