Aruco java, trying to get marker IDs [solved]

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we need to see the type of arucoIDs. how do you declare it ?

also, c++, java, python all start indexing at 0,not 1. if you only have 1 marker, (1,1) is probably invalid

Hi @berak,thanks for your answer. "arucoIDs" is a Mat type, declared at onCameraViewStarted as:

public Mat arucoIDs = new Mat();

First the app detect the Aruco markers using: Aruco.detectMarkers(imageAruco, dictionary, corners, arucoIDs);

Then it draws the detected markers using:

Aruco.drawDetectedMarkers(mRgba, corners, arucoIDs, new Scalar(0, 255, 0));

This is the Aruco.java code called from drawDetectedMarkers function:

//javadoc: drawDetectedMarkers(image, corners, ids, borderColor)
    public static void drawDetectedMarkers(Mat image, List<Mat> corners, Mat ids, Scalar borderColor)
    {
        Mat corners_mat = Converters.vector_Mat_to_Mat(corners);
        drawDetectedMarkers_0(image.nativeObj, corners_mat.nativeObj, ids.nativeObj, borderColor.val[0], borderColor.val[1], borderColor.val[2], borderColor.val[3]);

        return;
    }

please try to print out the shape/size of your arucoIDs

Using "putText" function I get these info:

Imgproc.putText(mRgba, "Aruco:"+ arucoIDs.get(0,0), new Point(30, 80), 3, 0.5, new Scalar(255, 0, 0, 255), 1);

 Imgproc.putText(mRgba, "Aruco:"+ arucoIDs.size(), new Point(30, 80), 3, 0.5, new Scalar(255, 0, 0, 255), 1);

That Aruco marker comes from the DICT_4X4_50 dictionary.

i bet with 2 markers, the next is at ids.get(0,1);, 0,2...0,3... etc.

I´ve solved the problem, I´ve got a String value using toString() function:

public void drawDetectedMarkers(Mat mRgba) {
        Aruco.drawDetectedMarkers(mRgba, corners, arucoIDs, new Scalar(0, 255, 0));

        Imgproc.putText(mRgba, "Aruco:"+ Arrays.toString(arucoIDs.get(0,0)), new Point(30, 80), 3, 0.5, new Scalar(255, 0, 0, 255), 1);
    }

Now I got this:

So from now, the robot can "decide" depending on the marker ID if it should turn left or right.

Maybe there is a way to get an integer value (5) instead of a double value (5.0?

Thanks berak.

Mat.get() returns a double[], whatever is in it. you're safe here to simply cast it like

int id = (int)(ids.get(i, 0)[0]);