Storing sensor_msgs::Image from cv_bridge

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The signatures for the method (from CvImage) are:

void                    toImageMsg (sensor_msgs::Image &ros_image)   const
sensor_msgs::ImagePtr   toImageMsg ()                                const

So we use the first option. And note that the image message is passed by reference. So you construct your message, let's say it's my_msg, and let's say the image that is a part of it is called img. If your CvImage object is my_cv_img then you would call:

my_cv_img.toImageMsg(my_msg.img);

And you are done. Note that toImageMsg allocates the memory for the image data itself, as can be seen by looking at the code for it: cv_bridge.cpp