Unity Button Without an Image?

I want to create a button whose clickable area is only specified by a BoxCollider with Unity’s new UI (similar to how you would do it from within NGUI). I can’t get a Unity Button to work without the presence of an Image component (which ultimately represents the clickable area of the button).

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As a workaround, can you use a transparent image?

This thread has an answer. Create a component that inherits Graphic, and use that instead of Image…