Help with calling a ros method

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Hi everyone, I have been trying to convert the following code on this tutorial link:text into .cpp and .h files. This is not an algorithm question as the code works when it is all in one .cpp file. Here is what I have so far in my .cpp file:

    //Code from <a href="http://siddhantahuja.wordpress.com/2011/07/20/working-with-ros-and-opencv-draft/">http://siddhantahuja.wordpress.com/2011/07/20/working-with-ros-and-opencv-draft/</a>
#include "../header/Webcam.h"
#include <iostream>

void Webcam::invertImage(cv_bridge::CvImagePtr cv_ptr){
 //Invert Image
    //Go through all the rows
    for(int i=0; i<cv_ptr->image.rows; i++)
    {
        //Go through all the columns
        for(int j=0; j<cv_ptr->image.cols; j++)
        {
            //Go through all the channels (b, g, r)
            for(int k=0; k<cv_ptr->image.channels(); k++)
            {
                //Invert the image by subtracting image data from 255               
                cv_ptr->image.data[i*cv_ptr->image.rows*4+j*3 + k] = 255-cv_ptr->image.data[i*cv_ptr->image.rows*4+j*3 + k];
            }
        }
    }
}

 void Webcam::imageCallback(const sensor_msgs::ImageConstPtr& camera_image)
{

//Store all constants for image encodings in the enc namespace to be used later.
namespace enc = sensor_msgs::image_encodings;

//Declare a string with the name of the window that we will create using OpenCV where processed images will be displayed.
static const char WINDOW[] = "Image Processed";

//Use method of ImageTransport to create image publisher
image_transport::Publisher pub;

    //Convert from the ROS image message to a CvImage suitable for working with OpenCV for processing
    cv_bridge::CvImagePtr cv_ptr;
    try
    {
        //Always copy, returning a mutable CvImage
        //OpenCV expects color images to use BGR channel order.
        cv_ptr = cv_bridge::toCvCopy(camera_image, enc::BGR8);
    }
    catch (cv_bridge::Exception& e)
    {
        //if there is an error during conversion, display it
        ROS_ERROR("camera::main.cpp::cv_bridge exception: %s", e.what());
        return;
    }

   //modify the image
   Webcam wc;
   wc.invertImage(cv_ptr);


    //Display the image using OpenCV
    cv::imshow(WINDOW, cv_ptr->image);
    //Add some delay in miliseconds. The function only works if there is at least one HighGUI window created and the window is active. If there are several HighGUI windows, any of them can be active.
    cv::waitKey(3);
    /**
    * The publish() function is how you send messages. The parameter
    * is the message object. The type of this object must agree with the type
    * given as a template parameter to the advertise<>() call, as was done
    * in the constructor in main().
    */
    //Convert the CvImage to a ROS image message and publish it on the "camera/image_processed" topic.
        pub.publish(cv_ptr->toImageMsg());
}

Here is the .h file:

//Includes all the headers necessary to use the most common public pieces of the ROS system.
#include <ros/ros.h>
//Use image_transport for publishing and subscribing to images in ROS
#include <image_transport/image_transport.h>
//Use cv_bridge to convert between ROS and OpenCV Image formats
#include <cv_bridge/cv_bridge.h>
//Include some useful constants for image encoding. Refer to: <a href="http://www.ros.org/doc/api/sensor_msgs/html/namespacesensor__msgs_1_1image__encodings.html">http://www.ros.org/doc/api/sensor_msgs/html/namespacesensor__msgs_1_1image__encodings.html</a> for more info.
#include <sensor_msgs/image_encodings.h>
//Include headers for ...