Revision history [back]

I'm attempting to implement image comparison in Unity3D using OpenCVForUnity.

I can't seem to filter matches and need some help.

From all the posts that I've read, I should be able to filter my matches between two images by using distance. However matches[i].distance doesn't seem to exist in the Unity plugin.

The following code will simply error out due to the missing call to 'distance'

  for( int i = 0; i < descriptors_1.rows; i++ )
  { double dist = matches[i].distance;
    if( dist < min_dist ) min_dist = dist;
    if( dist > max_dist ) max_dist = dist;
  }

So I ran a test on my matches.

        for (int i = 0; i < matches.cols (); i++)
        {
            for(int j = 0; j < matches.rows (); j++)
            {
                Debug.Log("Row " + i + " Column " + j + " Value " + matches.get(i,j));
            }
        }

The above always returns 'Row 0 Column 0 Value System.Double[]' for the first entry and 'Row 0 Column 1 Value ' for the following 499 entries.

I do see lines between the matches. However I see 500 lines regardless of the quality of the match. I guess that is expected as it's my duty to filter those matches (as I'm trying to do).

My entire code is:

    void Start ()
    {

        Texture2D imgTexture;
        if (Random.value < .5f)
            imgTexture = Resources.Load ("lena") as Texture2D;
        else
            imgTexture = Resources.Load ("triangular-face") as Texture2D;
        Texture2D imgTexture2 = Resources.Load ("lena") as Texture2D;

        Mat img1Mat = new Mat (imgTexture.height, imgTexture.width, CvType.CV_8UC3);
        Utils.texture2DToMat (imgTexture, img1Mat);
        Mat img2Mat = new Mat (imgTexture2.height, imgTexture2.width, CvType.CV_8UC3);
        Utils.texture2DToMat (imgTexture2, img2Mat);

        MatOfKeyPoint keypoints1 = new MatOfKeyPoint();
        MatOfKeyPoint keypoints2 = new MatOfKeyPoint();
        Mat descriptors1 = new Mat();
        Mat descriptors2 = new Mat();

        FeatureDetector detector = FeatureDetector.create(FeatureDetector.ORB); 
        DescriptorExtractor extractor = DescriptorExtractor.create(DescriptorExtractor.ORB);

        detector.detect(img1Mat, keypoints1);
        detector.detect(img2Mat, keypoints2);  

        extractor.compute(img1Mat, keypoints1, descriptors1);
        extractor.compute(img2Mat, keypoints2, descriptors2);

        DescriptorMatcher matcher = DescriptorMatcher.create (DescriptorMatcher.BRUTEFORCE_HAMMINGLUT);

        MatOfDMatch matches = new MatOfDMatch();
        matcher.match(descriptors1,descriptors2 ,matches);

        for (int i = 0; i < matches.cols (); i++)
        {
            for(int j = 0; j < matches.rows (); j++)
            {
                Debug.Log("Row " + i + "Column " + j + "Value " + matches.get(i,j));
            }
        }


        Mat resultImg = new Mat ();

        Features2d.drawMatches (img1Mat, keypoints1, img2Mat, keypoints2, matches, resultImg);

        Texture2D texture = new Texture2D (resultImg.cols (), resultImg.rows (), TextureFormat.RGBA32, false);

        Utils.matToTexture2D (resultImg, texture);

        gameObject.GetComponent<Renderer> ().material.mainTexture = texture;

    }