Can we perform on Mouse over even in sikuli

you have to simulate, what you yourself would do with mouse and/or keyboard (low level mouse and keyboard functions) to select any visual object.

as already mentioned: http://sikuli.org/blog/2010/05/06/extract-text-with-clipboard/

The principle for text:
- get a point on the screen, where you can start a select
- operate with mouse/keyboard to select the object
- use copy (e.g. ctrl-c) to get it on the clipboard
- use getClipboard() to get it in your script

If its a picture, you copy to clipboard, you don't have access to it directly in a script for now. You have to use an external helper, to produce a file from the clipboard picture, that you then can use in your script by its filename.