Can I take a screen capture from an Android app by using a service?

I was wondering if there is a way to take a scr开发者_运维知识库eenshot of the current screen inside the mobile phone using a service (I know how to do it through DDMS though)

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Not without root access.

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Just for encouragement I would like to say that on Android Developer Challenge 2 there is an application called 'drocap' that does exactly this - takes screenshots on the phone. This is running on my stock european Hero, so no root access required.

But I have no idea how it works. So - keep looking ;)