话不多说，直接上代码

#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/freetype.hpp>using namespace std;
using namespace cv;int main(void)
{Mat image(1000, 1800, CV_8UC3, Scalar(200,162,33));Ptr<freetype::FreeType2> ft2;ft2 = freetype::createFreeType2();ft2->loadFontData("./simhei.ttf", 0);ft2->putText(image, "中文显示", Point(500, 500),150, CV_RGB(255, 206, 57),FILLED, LINE_AA, true);imshow("提示", image);waitKey(0);
}

调用freetype库，载入ttf字体包，解决。
ttf包只要是中文的都可以，我这里用的是宋体(simhei.ttf)，在windows下拷贝过来的。
目录为：C:/Windows/fonts.

效果演示

CmakeList 参考

# cmakelists: demo
cmake_minimum_required (VERSION 3.8)
project (warning VERSION 1.0.0)find_package (OpenCV REQUIRED)
include_directories (${OpenCV_INCLUDE_DIRS})add_executable (warning main.cpp)
target_link_libraries (warning ${OpenCV_LIBS})