how to get the back image of a window?

We are building a program for visual impaired people, the aim is to replace some features of the screen, like colors, shapes or else. Currently, we have a full开发者_高级运维-screen window, we grab a snapshot of the screen (through the robot java library) and we reproduce it to the full-screen window. When we try to take the next screenshot, obviously the image we got refers to the current full-screen window. We need to get the back of the full-screen window, after an extensive research we had no success on find a way to do so.

Do you know of a library or a way to achieve this, possibly (but not necessarily) in java?

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If you are in Windows 7 you could

1) have Robot click the Rectangle in the lower right corner (to the right of the clock). This will minimize everything.

2) Then have Robot take the screenshot

3) have Robot click the Rectangle again, returning all app windows to previous state

4) have Robot take the other screenshot showing with apps open (if you like)

Robot can do this very fast, but it will interfere with any mouse movement that the user is doing.

You can achieve something similar in other versions of Windows by using right click on the task bar and then selecting "Show the Desktop" and "Show open Windows" to return to the original perspective.