Very useful. You need to disable the right-click zoom/fit function, because it's disturbing that the image gets resized while trying to save it with right-click and "Save as...".

Also, would be good if you implement some visual numbering showing the percentage of zooming.

Lastly, a rotate image (by 15 degrees) and a mirror function will be helpful as well. So many times I wanted to see some image mirrored left to right or upside-down, without the need to import the image to an external image editor.