With that said, the dependency on OpenCV seems entirely overkill. Surely Pillow would be a much more sensible dependency (with ImageDraw), as all you're doing with this package is drawing rectangles and labels, rather than handling any CV tasks?
For users of this library, OpenCV is pretty likely to already be installed anyway.
Another couple of reasons - OpenCV in my experience handles nonstandard images much better than Pillow (eg many channels, >8 bit). It also has a uniform Python/C++ interface so this could easily be ported if desired. I maintain a C++/Qt desktop annotation app and this would definitely be something to crib from for visualisation. Although in this case image loading could be done somewhere else and the library could just take a Numpy array.
Edit: turns out it's possible with a few extra steps, but it's not trivial. You need to handle ascender/descenders, etc: https://stackoverflow.com/questions/43060479/how-to-get-the-....
OpenCV will tell you the bbox of what it just drew.
I could've definitely used Pillow, but is there any tangible advantage to using Pillow over OpenCV?
Having OpenCV as a dependency means that if a project isn't already using OpenCV, this fairly minor (in terms of scale of functionality) utility library has a lot of baggage.
In terms of convolution of implementing it, there may be a little more effort in terms of figuring some offsets (e.g., path widths may extend bounds), but it shouldn't be anything excessive I don't think.