OpenCV img scan and show lines.

scanline.cpp

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

using namespace cv;

int main() {
  Mat img;
  img = imread("dave.jpeg", -1);
  
  Mat win = Mat::zeros(0, img.rows, CV_8UC3);
  
  for (size_t i = 0; i < img.rows; ++i) {
    win.push_back(img.row(i));
    imshow("scan", win);
    waitKey(100);
  }

  return 0;
}