The resize functions themselves only looked repetitive because they were forming an interface, which is why refactoring them away was wrong. But the math they performed is a perfectly valid target for cleaning the code.
The end result is of course a huge bag of small, pure functions, but they're easy to test and refactor so it's never an issue.
There are lot of ways/patterns for solving the same problem... but tearing apart an existing interface being used by others isn't a good start.
The best part about abstraction is that you can modify the underpinnings to be more flexible without hurting the rest. A good step would be to create more flexible math functions underneath, like you're saying, and leave the rest alone.
Afterwards, there can be deeper conversations with the team about how they want the interfaces to communicate to provide an obvious facade but an abstract implementation.