#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/opencv.hpp>
...
Mat img = imread("C:/Users/Пользователь/Desktop/1.png", CV_LOAD_IMAGE_COLOR);
namedWindow("Display window", WINDOW_AUTOSIZE);// Create a window for display.
imshow("Display window", img);