Day 8 - Opencv 用迭代器扫描图像

Day 8 - Opencv 用迭代器扫描图像

#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>
#include <random>
#include <iostream>

//减色函数
void reduceColor(cv::Mat image, int n);

int main(int argc, char** argv)
{
	cv::Mat image = cv::imread("15011.jpg");
	if (image.empty())
	{
		std::cout << "\n Durn, couldn't read image filename " << std::endl;
		return 1;
	}
	cv::namedWindow("Original Image");
	cv::imshow("Original Image", image);

	auto startTime = std::chrono::system_clock::now();
	reduceColor(image, 32);
	auto endTime = std::chrono::system_clock::now();
	std::cout << "time:" << std::chrono::duration_cast<std::chrono::microseconds>(endTime - startTime).count() << std::endl;
	cv::namedWindow("ReducedColr Image");
	cv::imshow("ReducedColr Image", image);
	cv::waitKey(0);
	return 0;
}


//image: 输入图像
//div    : 减色因子
void reduceColor(cv::Mat image, int div)
{
	double nTemp = std::log(static_cast<double>(div)) / std::log(2.0); //求解给定div下的n值 div = pow(2, n);
	int n = static_cast<int>(nTemp + 0.5); //0.5相当于四舍五入

	//掩码，求div的倍数
	uchar mask = 0xFF << n;
	uchar div2 = div >> 1;

	//创建迭代器
	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] &= mask;
		(*it)[0] += div2;
		(*it)[1] &= mask;
		(*it)[1] += div2;
		(*it)[2] &= mask;
		(*it)[2] += div2;
	}
}

通过迭代器的减色算法，运行速度比较慢， 46097us.