Make a chessboard pattern using OpenCV for camera calibration

makeChessboard.cpp

// Make a chessboard pattern given the num. of rows & cols, square size in pixels, and square colors 
void crvlMakeChessboardPattern(Mat &outChessboard, int inRows, int inCols, int inSquareSize = 100, Scalar color1 = CV_RGB(0, 0, 0), Scalar color2 = CV_RGB(255, 255, 255)){
	CV_Assert(inRows > 1 && inCols > 1);
	CV_Assert(inSquareSize > 0);

	int chessboardImgCols = inCols*inSquareSize;
	int chessboardImgRows = inRows*inSquareSize;
	outChessboard = Mat(chessboardImgRows, chessboardImgCols, CV_8UC3, Scalar(0, 0, 0));
	
	for (size_t rows = 0, rowNum = 0; rows < chessboardImgRows; rows += inSquareSize, rowNum++)
	{
		for (size_t cols = 0, colNum = 0; cols < chessboardImgCols; cols += inSquareSize, colNum++)
		{
			Rect rec(cols, rows, inSquareSize, inSquareSize);
			if ((rowNum + colNum) % 2 == 0)
				rectangle(outChessboard, rec, color1, -1, 8);
			else
				rectangle(outChessboard, rec, color2, -1, 8);
		}
	}
}

int main(){
	Mat chessboardImg;
	crvlMakeChessboardPattern(chessboardImg, 6, 8);
	imshow("Chessboard1", chessboardImg);
	imwrite("Chessboard1.bmp", chessboardImg);
	
	crvlMakeChessboardPattern(chessboardImg, 5, 7, 200, CV_RGB(255,0,0), CV_RGB(0,0,255));
	imshow("Chessboard2", chessboardImg);
	imwrite("Chessboard2.bmp", chessboardImg);
	
	waitKey(0);
}