Do you know the mailing services Viber, Whatsapp via API?

Question

API

The task before me is to make the integration of our program with the mailing service.
There are several conditions that must be met:
1) Working with Viber and Whatsapp is mandatory, but if there are more messengers, then it's okay)
2) Integration via API
3) The ability to send JPEG No matter how
much I searched, all services work either with different messengers, or without API

Answer 1

https://www.whatsapp.com/business/api
https://developers.viber.com/docs/api/
subscription business is the main and so far the only monetization tool for these chats, someone has to pay for storing and sending pictures and chats 2.5 and 0.8 billion people, respectively
, all other methods will work, simulating the work of a regular client, for example, through injecting web client scripts or simulating button presses (on android, almost standard functionality through adb or developing a plugin for people with disabilities)

Answer 2

We use GreenApi. But it's just for a wake-up call.