Great work Rated 5 out of 5 stars

I used to have to zoom in (whole page) to enlarge images and then zoom out, but this add-on eliminates all that.

The only thing that would make it better is perhaps to change the right click reset function so that users don't have to dismiss the context menu that pops up after resetting.
Maybe just change the double click function so that it resets the image back to default instead of enlarging it, especially considering that you're already providing a function for enlarging the image.

Updating my comment. Perhaps double click for reset (and full enlargement for that matter) isn't a good idea considering that some images are image links. :|
Perhaps a combination of right click plus a key?

In any event, it's a great and useful add-on and I thank you for developing it, and for making it a restartless one.

This review is for a previous version of the add-on (1.1.rev361). 

Thanks :)

I have uploaded version 1.2 which addresses your suggestion, considering how many people requested this, I had to do it, besides I like it that myself.

In version 1.2 LMB has been swapped with RMB. I have also deprecated the double click functionality as it caused issues, especially when seeing my mother use it haha :P However if you hold down CTRL and then click an image with the MMB(Middle Mouse Button) it'll still maximize the image, although this doesn't function very nice along with the reset function) I just put that in there just in case it's still wanted.