How to get image of wide-angle camera

Hello. I'd like to get a still image of a fisheye camera. So I am doing simulation using [Wide-Angle Camera](http://gazebosim.org/tutorials?tut=wide_angle_camera&branch=wideanglecamera#PluginExample) on Gazebo. However, unlike other cameras such as [Openni Kinect](http://gazebosim.org/tutorials?tut=ros_gzplugins), it does not describe how to write Topic to send image information. How should I write? Thank you.