Stitch Line appears to be perfect. This version does not have a watermark. The app is fully functional. You can try it for free.
Original calibration Image
Hold the camera sideways and face the lens toward the sky. One lens points to the ground. Take the image outside where there are distant objects like trees.
Calibration Points
Select distant objects to calibrate the lenses. This is a one-time calibration and the lens calibration is saved to your mobile phone. The next time, you just stitch it.
Stitched Image
With settings saved. No additional calibration.
it’s raining today.
I think the bend is actually a bend in my rain gutter.
Stitched Area
The stitch looks close to perfect to me.