Split image into parts(px)?

Question

ruby

There is a large image on which there will be icons, I want to make it so that:
1. Clicked on the image
2. A large image opened
3. Selected an icon on this image
4. Got (I don’t know what to call it correctly here) the background-position of this icon on the image
5 .Added this value to php variable.
Tell me, please, what libraries are there or give me an idea.

Answer 1

Do you have to reinvent the wheel?
Or you can use the good old ?

Answer 2

htmlbook.ru/html/area