Custom content size in each scale level and option for adding an annotation.

[bibinjacobpulickal]

This is a request, Finding this repository just saved my day. It was quite hard to find this repository. This was the best I could find for my requirement.
My request is to add the possibility of adding custom content size in each layer ie., if an image is of content size 15000x15000 and when zoomed-in the content size is 20000x20000 instead of 30000x30000. Like having intermediate zoom levels for more precision.
Also, and option to add annotation where the user taps and add a custom message on the annotation. Annotation should include other types like line drawing or drawing a circle/box. Also, and option to measure the length or area of selected annotation should be able to calculate if the length and area of a tile is provided.