Error when try to get undistorted images after camera calibration and adding camera matrix and distortion coefficients

Question

I've used the sample OpenCV program to calculate the camera matrix and distortion coefficients from my camera and produced an xml file with the relevant data. No I would like to correct distortion in some images taken from the same camera. So I create the program but still got some error. I'm trying to use it to get undistort image.

Here is my code

#include <iostream>
#include <sstream>
#include <string>
#include <ctime>
#include <cstdio>
#include <opencv2/core.hpp>
#include <opencv2/core/utility.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/calib3d.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
#include "cameracalibrator.h"

CameraCalibrator::CameraCalibrator() :
    flag(0),
    mustInitUndistort(true)
{
}

using namespace cv;
using namespace std;

int main(){
Mat src,gray,image;

Mat cameraMatrix = (Mat1d(3, 3) <<  8.5033354550764898e+002, 0, 640, 0, 8.5033354550764898e+002, 360, 0, 0, 1);
Mat distortionCoefficients = (Mat1d(1, 5) << -4.2796890539434634e-001, 2.8770882755049054e-001, 0, 0, -1.4405356460809188e-001);

// remove distortion in an image (after calibration)
cv::Mat CameraCalibrator::remap(const cv::Mat &image) {

    cv::Mat undistorted;
    cv::Mat image=imread("C:/Users/NTU/Desktop/Test/im4.png");

    if (mustInitUndistort) { // called once per calibration

        cv::initUndistortRectifyMap(
            cameraMatrix,  // computed camera matrix
            distCoeffs,    // computed distortion matrix
            cv::Mat(),     // optional rectification (none) 
            cv::Mat(),     // camera matrix to generate undistorted
//          cv::Size(640,480),
            image.size(),  // size of undistorted
            CV_32FC1,      // type of output map
            map1, map2);   // the x and y mapping functions

        mustInitUndistort= false;
    }

    // Apply mapping functions
    cv::remap(image, undistorted, map1, map2, 
        cv::INTER_LINEAR); // interpolation type

    return undistorted;

imshow("gg",undistorted);
while(uchar(waitKey(1))!='Q');
//return 0;
}
}

when run got this error :

error: qualified-id in declaration before '(' token
 cv::Mat CameraCalibrator::remap(const cv::Mat &image) {

Any help?