Aruco custom dictionary

[ekkelenkamp]

System information (version)

• OpenCV => 4.4.3
• Operating System / Platform => Windows 64 Bit, Java binding
• Compiler => Visual Studio 2019

Detailed description

I'm trying to create an Aruco custom dictionary using the java binding. When drawing the image, it doesn't match the configured marker. I cannot find any examples on how to do this in java.

I configured a marker like:
011
111
011

But I get as result:

011
110
010

Steps to reproduce

Here a simple test case:

  
    @Test
    public void testGithub() {
        byte[][] marker = {{0,1,1},{1,1,1},{0,1,1}};
        Dictionary dictionary = Dictionary.create(1, 3);
        dictionary.set_maxCorrectionBits(0);
        Mat markerBits = new Mat(3, 3, CV_8UC1);
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                markerBits.put(i, j, marker[i][j]);
            }
        }
        Mat markerCompressed = Dictionary.getByteListFromBits(markerBits);
        dictionary.get_bytesList().push_back(markerCompressed);
        Mat markerMat = new Mat(3, 3, CV_8UC1);
        Aruco.drawMarker(dictionary, 0, 9, markerMat);
        Imgcodecs.imwrite("c:/temp/marker0.jpg", markerMat);
    }

Resulting marker is attached.

[ekkelenkamp]

What i noted is that the dictionary.get_bytesList() is already filled with a random marker directly after the Dictionary has been created. This results in adding a new marker not being updated.
This differs from the c++ implementation. I use similar code from ios and there it works just fine. For example:

   unsigned char data[3][3] = { {0,1,0},{0,1,1},{1,1,0} };
    cv::Mat markerBits = cv::Mat(3, 3, CV_8UC1, data);
    cv::Mat markerCompressed = cv::aruco::Dictionary::getByteListFromBits(markerBits);
    dictionary->bytesList.push_back(markerCompressed);

So I probably can change the values in the already configured dictonary entries, but it looks like a bug to me in the java binding.

[ekkelenkamp]

I can confirm that overwriting the values of the existing dictionary is working. Here the testcase that fixes this issue.

    @Test
    public void testGithub() {
        char[][] marker = {{0,1,1},{1,1,1},{0,1,1}};
        Dictionary dictionary = Dictionary.create(1, 3);
        dictionary.set_maxCorrectionBits(0);
        Mat markerBits = new Mat(3, 3, CV_8UC1);
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                markerBits.put(j, i, marker[j][i]);
            }
        }
        Mat markerCompressed = Dictionary.getByteListFromBits(markerBits);
        Mat dictionaryMat = dictionary.get_bytesList();
        int markerId = 0;
        for (int i = 0; i < 2; i++) {
            double[] markerValues = markerCompressed.get(0, i);
            byte[] b = new byte[4];
            for (int m = 0; m < markerValues.length; m++) {
                b[m] = (byte) markerValues[m];
            }
            dictionaryMat.put(markerId, i, b);
        }
        Mat markerMat = new Mat(3, 3, CV_8UC1);
        Aruco.drawMarker(dictionary, 0, 9, markerMat);
        Imgcodecs.imwrite("/tmp/aruco/marker0.jpg", markerMat);
    }

Now the generated marker is as expected.

[AleksandrPanov]

related: #3200

[AleksandrPanov]

@ekkelenkamp Dictionary.create() call generateCustomDictionary() inside.
use set_bytesList() to change bytesList:

        byte[][] marker = {{0,1,1},{1,1,1},{0,1,1}};
        Dictionary dictionary = Dictionary.create(1, 3);
        dictionary.set_maxCorrectionBits(0);
        Mat markerBits = new Mat(3, 3, CvType.CV_8UC1);
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                markerBits.put(i, j, marker[i][j]);
            }
        }
        Mat markerCompressed = Dictionary.getByteListFromBits(markerBits);
        dictionary.set_bytesList(markerCompressed);