如何在Mat中找到指定的值，并在另一个Mat中找到其对应的值

Question

如果我有一个Mat的像素值，我如何在另一个Mat中找到相同像素值的位置（坐标）？

Answer 1

以下内容提供find()，它会将特定值的Mat中的位置作为点向量返回。简短的演示main()表明它适用于彩色和灰度图像。

#include <opencv2/core/core.hpp>
#include <iostream>     // std::cout
#include <vector>       // std::vector

template<typename _Tp>
std::vector<cv::Point> inline find(_Tp key, cv::Mat M)
{
    int pos = 0;
    std::vector<cv::Point> result;
    std::for_each(M.begin<_Tp>(), M.end<_Tp>(), [&](_Tp & m)
    {
        if(m == key)
        {
            cv::Point p(pos % M.cols, pos / M.cols);
            result.push_back(p);
        }
        pos ++;
    });

    return result;
}


int main(int argc, char** argv)
{
    uchar data[] = {1, 2, 3,  4, 5, 6, 8, 9, 0,
                    8, 9, 0,  4, 5, 6,   1, 2, 3, 
                    1, 2, 3,  8, 9, 0, 4, 5, 6,
                    7, 8, 9,  3, 4, 5, 3, 4, 5};

    cv::Mat M1(4, 9, CV_8UC1, data);
    uchar key1(1);

    std::vector<cv::Point> vp = find(key1, M1);

    std::cout << "key " << int(key1) << " was found in the Mat" << std::endl;
    std::cout << M1 << std::endl  << "at" << std::endl;
    for(cv::Point p : vp)  // print where key is found in M
    {
        std::cout << p << std::endl;
    }

    cv::Mat M3(4, 3, CV_8UC3, data);
    cv::Vec3b key3(8, 9, 0);

    vp = find(key3, M3);

    std::cout << std::endl;
    std::cout << "key " << key3 << " was found in the Mat" << std::endl;
    std::cout << M3 << std::endl  << "at" << std::endl;
    for(cv::Point p : vp)  // print where key is found in M
    {
        std::cout << p << std::endl;
    }

    return 0;
}