Image SMS uses long text SMS to send a very small picture (NOT MMS or Internet). It uses base64 technique (similar to a email attachment) to transfer data. It is a bare metal App and Open Source on github. If you want to enlarge the features, you have to do it by your own!
I love my privacy. Thus I love apps with only a couple of permissions. Image SMS needs only access on:
*SMS (read and send)
*Camera
Image SMS does not use access to:
*Files
*Contacts
*Internet
This may be strange to you, because you need a phone number and there is no contact selection.