OPENCV学习笔记11_编写高效的图像扫描循环

//Test running time，edited by yunfung
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
using namespace cv;
using namespace std;

void colorReduce1(Mat& image, int div = 64)
{
    for (int i = 0; i < image.rows; i++)
    {
         for (int j = 0; j < image.cols; j++)
        {
            image.at<Vec3b>(i, j)[0] = image.at<Vec3b>(i, j)[0] / div*div + div / 2;
            image.at<Vec3b>(i, j)[1] = image.at<Vec3b>(i, j)[1] / div*div + div / 2;
            image.at<Vec3b>(i, j)[2] = image.at<Vec3b>(i, j)[2] / div*div + div / 2;
        }
    }
}

void colorReduce2(cv::Mat image, int div = 64) {
    int nl = image.rows;
    int nc = image.cols * image.channels();
    for (int j = 0; j < nl; j++) {
        uchar* data = image.ptr<uchar>(j);
        for (int i = 0; i < nc; i++) {
            data[i] = data[i] / div*div + div / 2;

        }
    }
}

void colorReduce3(cv::Mat &image, int div = 64) {
    if (image.isContinuous()){
        image.reshape(1, 1);
    }
    int nl = image.rows;
    int nc = image.cols * image.channels();
    for (int j = 0; j < nl; j++) {
        uchar* data = image.ptr<uchar>(j);
        for (int i = 0; i < nc; i++) {
            data[i] = data[i] / div*div + div / 2;
        }
    }
}

void colorReduce4(cv::Mat &image, int div = 64) {
    cv::Mat_<cv::Vec3b>::iterator it = image.begin<cv::Vec3b>();
    cv::Mat_<cv::Vec3b>::iterator itend = image.end<cv::Vec3b>();
    for (; it != itend; ++it) {
        (*it)[0] = (*it)[0] / div * div + div / 2;
        (*it)[1] = (*it)[1] / div * div + div / 2;
        (*it)[2] = (*it)[2] / div * div + div / 2;
    }
}

void calrunTime(int v, Mat&image)
{
    double duration;
    duration = static_cast<double>(getTickCount()); //强制转化为double
    for (int i = 0; i < 10; i++)
    {
        switch (v)
        {
        case 1:
            colorReduce1(image);   //at
            break;
        case 2:
            colorReduce2(image);   //pointers
            break;
        case 3:
            colorReduce3(image);   //reshape(continuous)
            break;
        case 4:
            colorReduce4(image);   //iterators
            break;
        default:
            break;
        }
    }
    duration = static_cast<double>(getTickCount()) - duration;
    duration /= getTickFrequency();
    duration *= (1000/10); //average
    cout << "duration" << v << " : " << duration << "mS"<< endl;
}

int main()
{
    Mat image = imread("test.jpg");
    Mat imageClone = image.clone();
    cout << "yunfung_opencv_learn_test:" <<"\n\n";
    calrunTime(1, image);

    image = imread("test.jpg");
    imageClone = image.clone();
    calrunTime(2, image);
    image = imread("test.jpg");
    imageClone = image.clone();
    calrunTime(3, image);
    image = imread("test.jpg");
    imageClone = image.clone();
    calrunTime(4, image);

    namedWindow("Image Result");
    imshow("Image Result", imageClone);
    waitKey();
    return 0;
}