Instamax
v2.0, requires Apple Shortcuts on iOS 12
The skinniest aspect ratio that Instagram supports is 4x5. If your image is taller, Instagram will crop it, destroying your soul.
Instamax preserves your entire photo and pads it on the sides with white, so that it will fit perfectly on the ’gram.
Launch Instamax directly and chose a photo, or run it as an extension and send photos to it from the Photos app.
Changelog
Instamax 1.0 released.
2.0 Padded images are now saved at the original resolution plus the padding, rather than shrunk to IG’s max res.