Aruco tutorial code does not compile - opencv

Question

Hello I am getting an error when using aruco. I am just trying to get an example from the tutorial working. I did everything according to the tutorial but I get:
/home/pi/Programs/markerDetection/markerDetection.cpp: In function ‘int main(int, char**)’:
/home/pi/Programs/markerDetection/markerDetection.cpp:26:104: error: invalid initialization of reference of type ‘cv::Ptr<cv::aruco::Dictionary>&’ from expression of type ‘cv::aruco::Dictionary’
aruco::detectMarkers(inputImage, dictionary, markerCorners, markerIds, parameters, rejectedCandidates);
^
In file included from /home/pi/Programs/markerDetection/markerDetection.cpp:6:0:
/home/pi/opencv/include/opencv2/aruco.hpp:176:19: note: in passing argument 2 of ‘void cv::aruco::detectMarkers(cv::InputArray, cv::Ptr<cv::aruco::Dictionary>&, cv::OutputArrayOfArrays, cv::OutputArray, const cv::Ptr<cv::aruco::DetectorParameters>&, cv::OutputArrayOfArrays)’
CV_EXPORTS_W void detectMarkers(InputArray image, Ptr<Dictionary> &dictionary, OutputArrayOfArrays corners,
^
CMakeFiles/marker.dir/build.make:54: recipe for target 'CMakeFiles/marker.dir/markerDetection.cpp.o' failed
make[2]: *** [CMakeFiles/marker.dir/markerDetection.cpp.o] Error 1
CMakeFiles/Makefile2:60: recipe for target 'CMakeFiles/marker.dir/all' failed
make[1]: *** [CMakeFiles/marker.dir/all] Error 2
Makefile:76: recipe for target 'all' failed
make: *** [all] Error 2
My code is:
#include "opencv2/opencv.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/videoio/videoio.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/aruco.hpp"
#include <vector>
using namespace cv;
using namespace std;
int main (int argc, char** argv)
{
VideoCapture cap;
if(!cap.open(0)){
return 0;
}
for(;;){
Mat inputImage;
cap >> inputImage;
vector< int > markerIds;
vector< vector<Point2f> > markerCorners, rejectedCandidates;
aruco::DetectorParameters parameters;
aruco::Dictionary dictionary = aruco::getPredefinedDictionary(aruco::DICT_6X6_250);
aruco::detectMarkers(inputImage, dictionary, markerCorners, markerIds, parameters, rejectedCandidates);
Mat outputImage;
aruco::drawDetectedMarkers(outputImage, markerCorners, markerIds);
if(inputImage.empty()) break;
imshow("Webcam", outputImage);
if(waitKey(1) >= 0) break;
}
return 0;
}
I know there are too many includes and the code needs some work but I just need it to compile and I have no idea what is happening there. Has the function changed?

Answer 1

The following code works for me:
Dictionary declaration:
cv::Ptr<cv::aruco::Dictionary> dictionary = cv::aruco::getPredefinedDictionary(cv::aruco::DICT_6X6_250);
As the function getPredefinedDictionary returns a Ptr<Dictionary>
(http://docs.opencv.org/trunk/d9/d6a/group__aruco.html)
To detect markers:
cv::aruco::detectMarkers(gray, dictionary, marker_corners, marker_ids);

Answer 2

I had the same problem as you. Here is what did the trick:
instead of:
aruco::DetectorParameters parameters;
aruco::Dictionary dictionary=aruco::getPredefinedDictionary(aruco::DICT_6X6_250);
use:
cv::Ptr<aruco::DetectorParameters> parameters;
cv::Ptr<aruco::Dictionary> dictionary=aruco::getPredefinedDictionary(aruco::DICT_6X6_250);
I hope it helps you.

Answer 3

I was missing some include files. These are the ones I have now:
#include "opencv2/aruco.hpp"
#include <iostream>
#include <stdio.h>
#include <opencv2/highgui.hpp>
#include "opencv2/imgcodecs.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/core.hpp"
#include "opencv2/videoio/videoio.hpp"
#include <vector>
And the libraries are (these are included in Project-> Properties->settings->Linker->Input ):
opencv_core450.lib
opencv_highgui450.lib
opencv_objdetect450.lib
opencv_videoio450.lib
opencv_imgproc450.lib
opencv_imgcodecs450.lib
opencv_aruco450.lib
opencv_core450d.lib
opencv_highgui450d.lib
opencv_objdetect450d.lib
opencv_videoio450d.lib
opencv_imgproc450d.lib
opencv_imgcodecs450d.lib
opencv_aruco450d.lib
The opencv_aruco450.lib was not getting properly saved as far as I know. This was my problem.