Implement UX for sending image attachments

When the message field is empty, there's an image icon to attach an image:

Clicking it opens the system file selector:

If chosen image is shown as a preview, with an option to cancel the operation and to add an image caption:

A seascape image shows a black/grey or color picked from the image on the sides:

Edited Dec 13, 2018 by Torsten Grote