opencv c++ （3）：像素操作4

像素的mean，std，min，max以及统计的方法

//像素基本操作
#include <iostream>
#include<opencv.hpp>
#include<opencv2\highgui\highgui.hpp>

using namespace std;
using namespace cv;

int main()
{
    
    


	Mat src = imread("src.jpg");

	if (src.empty())
	{
    
    
		printf("open file failed");
		return -1;
	}

	//1. 最大最小值 只支持单通道
	// 分离通道
	vector<Mat> channels;
	split(src, channels);
	imshow("B", channels[0]);
	// 最大最小值
	double min, max;
	// 最大最小值的坐标
	Point minLoc, maxLoc;

	minMaxLoc(channels[0], &min, &max, &minLoc, &maxLoc);
	cout << min << endl << max << endl << minLoc << endl << maxLoc;
	//2. 均值标准差，这个支持3通道
	//mean函数
	Scalar m = mean(src);
	Mat mm, ss;
	meanStdDev(src, mm, ss);
	cout << m << endl << mm << endl << ss;

	//3. 统计像素值
	vector<int>hist(256, 0);
	vector<int>hist2(256, 0);
	auto data = src.data;
	for (int row = 0; row < src.rows; row++)
	{
    
    
		uchar* src_row = src.ptr<uchar>(row);
		
		for (int col = 0; col < src.cols; col++)
		{
    
    	
			//data指针方式
			int pv = *data++; //B
			hist[pv]++;
			pv = *data++;    //G
			hist[pv]++;
			pv = *data++;   //R
			hist[pv]++;

			//ptr指针方式
			int pv2 = *src_row++;
			hist2[pv2]++;
			pv2 = *src_row++;
			hist2[pv2]++;
			pv2 = *src_row++;
			hist2[pv2]++;

		}
	}
	//data指针和ptr指针遍历结果一样
	cout << endl << "0:" << hist[0] << endl << "255:" << hist[255];
	cout << endl << "0:" << hist2[0] << endl << "255:" << hist2[255];
	waitKey(0);
	destroyAllWindows();
	return 0;
}

这里分别举例了data指针和ptr指针的用法