C++ 查找 cv::Mat 的最大值
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Find maximum value of a cv::Mat
提问by Ríomhaire
I am trying to find the maximum pixel value of a cv::Mat.
我试图找到 a 的最大像素值cv::Mat。
The Problem : *maxValueis always returning 0.
问题：*maxValue总是返回0。
From this S.O. thread, I understand that 'max_elementreturn iterators, not values. This is why I use *maxValue'
从这个 SO thread，我明白'max_element返回迭代器，而不是值。这就是为什么我使用*maxValue'
cv::Mat imageMatrix;
double sigmaX = 0.0;
int ddepth = CV_16S; // ddepth – The desired depth of the destination image
cv::GaussianBlur( [self cvMatFromUIImage:imageToProcess], imageMatrix, cv::Size(3,3), sigmaX);
cv::Laplacian(imageMatrix, imageMatrix, ddepth, 1);
std::max_element(imageMatrix.begin(),imageMatrix.end());
std::cout << "The maximum value is : " << *maxValue << std::endl;
Note : If min_elementis substituted in place of max_element, and minValuein place of maxValue, *minValuewill always return 0.
注意：如果min_element被替换为代替max_element，并且minValue代替maxValue，*minValue将始终返回0。
回答by shivakumar
You should use the OpenCV built-in function minMaxLocinstead of stdfunction.
您应该使用 OpenCV 内置函数minMaxLoc而不是std函数。
Mat m;
//Initialize m
double minVal;
double maxVal;
Point minLoc;
Point maxLoc;
minMaxLoc( m, &minVal, &maxVal, &minLoc, &maxLoc );
cout << "min val: " << minVal << endl;
cout << "max val: " << maxVal << endl;
