Hi Shalini, you'll likely have to create your own service as far as I know there's no OOTB service to take snapshots.
1. Create a custom extension using ThingWorx Extension SDK
2. In custom extension include the library that can allow you to to traverse through different DOMs on the webpage, something like HTML2Canvas
(side note : i think this question too sort of comes close to your description, but it sounds like you want to automate the the screenshots in which case above mentioned library would likely be more meaningful)
3. Build the extension and install it in your ThingWorx instance, you'll then be able to call that as a service or a widget depending what you are building.
Adding this thread as an additional resource if you are looking to build custom extension Thingworx custom widgets