Copy rows to matrix crashes OpenCV - Visual Studio 2010 C++ - c++

Question

I am trying to copy certain rows from src image to new image called gaps. The gaps image will contain only few rows. However the program crashes at the line with copyTo. The Mat src image is correct, it contains my image because I can view it by imshow().
Mat gaps;
int gap = 6;
for (int r = 0; r < src.rows; r++)
{
if ( r % gap == 0 )
src.row(r).copyTo(gaps.row(r));
}
imshow("gaps", gaps);
waitKey(0);
I am using OpenCV, Visual Studio 2010 C++ on Windows XP.
I tried to add this:
gaps.create(CV_8UC3, 2056,2056); to specify depth and dimensions but it still crashes.

Answer 1

Try this:
// if you want your background to be black --> Scalar(0,0,0)
Mat gaps = Mat(src.size(), src.type(), Scalar(0,0,0));
This is what you'll get, I don't know if that is what you expect/want.
Code
// set your input image
Mat src = imread("{path to input image}");
// your code with the change I proposed
Mat gaps = Mat(src.size(), src.type(), Scalar(0,0,0));
int gap = 6;
for (int r = 0; r < src.rows; r++) {
if ( r % gap == 0 )
src.row(r).copyTo(gaps.row(r));
}
imshow("gaps", gaps);
// create the result image
Mat result = Mat(Size(src.cols * 2, src.rows), src.type(), Scalar(0,0,0));
src.copyTo(result(Rect(0,0,src.cols,src.rows)));
gaps.copyTo(result(Rect(src.cols,0,src.cols,src.rows)));
imshow("result", result);
waitKey();