Open QR Code is an open-source, cross-platform app
...Users can generate QR codes from any text input, save them to their gallery, share them directly from the app, and scan QR codes to retrieve encoded information. Whether you're on Android, Windows, or the Web, you can create and share QR codes or scan them with a single click.
This is a reprository of software I have written. It is written in C, C++ and hopefully in some obscure Basic :-) I gladly share my stuff with you under the MIT license, so you can do what you want with it (almost)... :-)