markit is a simple tool to watermark images, on desktop and android devices.
Currently, watermarks must be in png format, and images in jpg.
markit is written in Go, using the Fyne toolkit. To build, you will need a working Go compiler with CGO, and the dependencies for Fyne. Please see https://developer.fyne.io/started/#prerequisites for those.
Once you have them, installing is as simple as:
go install github.com/wltechblog/markit@latest
Android builds and other cross compiling are done with fyne-cross, see https://github.com/fyne-io/fyne-cross