API
最大值和最小值
CV_EXPORTS_W void minMaxLoc(InputArray src, CV_OUT double* minVal,
CV_OUT double* maxVal = 0, CV_OUT Point* minLoc = 0,
CV_OUT Point* maxLoc = 0, InputArray mask = noArray());
- 参数一：src，单通道输入图像；
- 参数二：minVal，最小值；
- 参数三：maxVal，最大值；
- 参数四：minLoc，最小值坐标；
- 参数五：maxLoc，最大值坐标；
- 参数六：mask，掩码，通过此参数可以设置极值的查找范围。
均值
CV_EXPORTS_W Scalar mean(InputArray src, InputArray mask = noArray());
参数一：src，通道数为 1 到 4 个的输入图像；
参数二：mask，掩码，通过此参数可以设置求平均值的范围。
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\begin{array}{l} N = \sum _{I: \; \texttt{mask} (I) \ne 0} 1 \\ M_c = \left ( \sum _{I: \; \texttt{mask} (I) \ne 0}{ \texttt{mtx} (I)_c} \right )/N \end{array}
N=∑I:mask(I)=01Mc=(∑I:mask(I)=0mtx(I)c)/N
标准差
CV_EXPORTS_W void meanStdDev(InputArray src, OutputArray mean, OutputArray stddev,
InputArray mask=noArray());
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参数一：src，通道数为 1 到 4 个的输入图像；
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参数二：mean，均值；
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参数三：stddev，标准差；
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参数四：mask，掩码，通过此参数可以设置极值的查找范围。
N = ∑ I , mask ( I ) ≠ 0 1 mean c = ∑ I : mask ( I ) ≠ 0 src ( I ) c N stddev c = ∑ I : mask ( I ) ≠ 0 ( src ( I ) c − mean c ) 2 N \begin{array}{l} N = \sum _{I, \texttt{mask} (I) \ne 0} 1 \\ \texttt{mean} _c = \frac{\sum_{ I: \; \texttt{mask}(I) \ne 0} \texttt{src} (I)_c}{N} \\ \texttt{stddev} _c = \sqrt{\frac{\sum_{ I: \; \texttt{mask}(I) \ne 0} \left ( \texttt{src} (I)_c - \texttt{mean} _c \right )^2}{N}} \end{array} N=∑I,mask(I)=01meanc=N∑I:mask(I)=0src(I)cstddevc=N∑I:mask(I)=0(src(I)c−meanc)2
示例
#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/imgcodecs/imgcodecs.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
using namespace std;
int main() {
cout << CV_VERSION << endl;
Mat lena = imread("../image/lena.tif", IMREAD_ANYCOLOR);
Mat lenaGray = imread("../image/lena.tif", IMREAD_GRAYSCALE);
double min, max;
Point minLoc, maxLoc;
minMaxLoc(lenaGray, &min, &max, &minLoc, &maxLoc);
cout << "最小值：" << min << ", 位于：" << minLoc << endl;
cout << "最大值：" << max << ",位于：" << maxLoc << endl;
Scalar scalar = mean(lena);
cout << "平均值：" << scalar << endl;
Mat meanMat,stdDevMat;
meanStdDev(lena, meanMat, stdDevMat);
cout << "平均值：" << meanMat << endl;
cout << "标准差：" << stdDevMat << endl;
waitKey(0);
return 0;
}