#include <opencv2\core\core.hpp>

#include <opencv2\highgui\highgui.hpp>

#include <opencv2\imgproc\imgproc.hpp>

#include <iostream>

void colorReduce(cv::Mat& image, int div=)

{

    int nr = image.rows;

    int nc = image.cols * image.channels();

    int n = static_cast<int>( cv::log(static_cast<double>(div)) / cv::log(2.0) );

    uchar mask = 0xFF << n;

    for(int i=; i<nr; i++)

    {

        uchar* data = image.ptr<uchar>(i);

        for(int j=; j<nc; j++)

        {

            //*data++ = *data - *data % div + div / 2;

            *data++ = (*data & mask) + div / ;

        }

    }

}

int main(int argc, char** argv)

{

    cv::Mat img = cv::imread("F:\\images\\boldt.jpg");

    cv::Mat img2 = img.clone();    

    double duration;

    duration = static_cast<double>(cv::getTickCount());

    colorReduce(img2);

    duration = static_cast<double>(cv::getTickCount()) - duration;

    duration /= cv::getTickFrequency();

    cv::namedWindow("original");

    cv::imshow("original", img);

    cv::namedWindow("altered");

    cv::imshow("altered", img2);

    std::cout << duration << std::endl;

    cv::waitKey();

    return ;

}