Area resizing unreliable and limited when zoomed in a lot

[fredcooke]

At normal full-photo scale it works as you'd expect, however the more you zoom in and the smaller things get the harder it gets to get the area to resize and it seems like it runs into arbitrary limitations where it cannot be made smaller and other odd behaviour.

Expected behaviour:

Identical selection manipulation at any scale

Use case:

I use obscuracam for removing numberplates from photos of cars, often these are small in the photo but still readable - I only want to redact the minimum amount to keep the image looking good.

Possible flaw:

Perhaps bad scaling math is being used and errors get excessive?
Perhaps lower limit of selection size is being arbitrarily enforced with hard coded numbers?
Bugs in libraries being used?