HOW TO USE OPENCV IN GROOVY？ [closed]

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Hi all, I'm learning how to use opencv in ROS, following the tutorial

http://www.ros.org/wiki/cv_bridge/Tutorials/UsingCvBridgeToConvertBetweenROSImagesAndOpenCVImages

However, in the example, I was confused about the several QUESTIONS:

In the example, there is just one cpp file, does it be used as two nodes(including the publisher as well as the subscriber)?

Following the tutorial,I was going to build the node, however, at the last step, something wrong happened:

/home/tishiba/practice_no1/src/practice_no1_1/src/cv.cpp: In constructor ‘ImageConverter::ImageConverter()’:
/home/tishiba/practice_no1/src/practice_no1_1/src/cv.cpp:23:32: error: expected primary-expression before ‘/’ token
/home/tishiba/practice_no1/src/practice_no1_1/src/cv.cpp:23:33: error: ‘camera’ was not declared in this scope
/home/tishiba/practice_no1/src/practice_no1_1/src/cv.cpp:23:40: error: ‘rgb’ was not declared in this scope
/home/tishiba/practice_no1/src/practice_no1_1/src/cv.cpp:23:44: error: ‘image_color’ was not declared in this scope
make[2]: *** [practice_no1_1/CMakeFiles/cv.dir/src/cv.cpp.o] Error 1
make[1]: *** [practice_no1_1/CMakeFiles/cv.dir/all] Error 2
make: *** [all] Error 2
Invoking "make" failed
![image description](http://)

I wonder if I didn't include all the header file in the cpp file, now in my cpp file ,I had include header files as followed:

include <ros/ros.h>
include <image_transport/image_transport.h>
include <cv_bridge/cv_bridge.h>
include <sensor_msgs/image_encodings.h>
include <opencv2/imgproc/imgproc.hpp>
include <opencv2/highgui/highgui.hpp>

..NOW WHAT SHOULD I DO? NEED HELP ! THX!