CrossCam is a cross-platform what-you-see-is-what-you-get stereoscopic 3D cross view camera mobile app.
iOS: https://itunes.apple.com/app/id1436262905
Android: https://play.google.com/store/apps/details?id=com.kra2008.crosscam
SkiaSharp for the bitmap image editing: https://github.com/mono/SkiaSharp
OpenCV for the automatic alignment: https://opencv.org/
Emgu CV for the C#/Xamarin wrappers for OpenCV: http://www.emgu.com
Satya Mallick for this blog post that led me to OpenCV: https://www.learnopencv.com/image-alignment-ecc-in-opencv-c-python/
Testers on the CrossView subreddit: https://old.reddit.com/r/CrossView/