Overlaying image on Android [closed]

asked 2019-06-27 19:06:05 -0500

I've been trying to overlay an image over a rectangle detected by the camera. I'm using a function that is returning the path of my image from my sd card (.jpg), but it looks that it is not loading it correctly, or at least I can't display it where I want.

First of all, I check if the image is loaded (and I load it if it isn't). Then, I proceed recognizing rectangles. Once I recognize one, I'm suppose to overlay that rectangle on the frame with the loaded image, and then return to the ImageView the modified frame.

I'll share with you my code from the onCameraFrame function ("image" is a Mat object where I store my loaded image from my sdcard, and "img_path" is the string where the image's path is stored):

   Mat dst = inputFrame.rgba();
   //Here I check if the image is loaded

    if (image.empty()){

        image = imread(img_path, CV_LOAD_IMAGE_UNCHANGED);

    } else {

        //If the image is loaded, then I proceed to process the frame.
        Mat gray = inputFrame.gray();

        pyrDown(gray, dsIMG, new Size(gray.cols() / 2, gray.rows() / 2));
        Imgproc.pyrUp(dsIMG, usIMG, gray.size());

        Imgproc.Canny(usIMG, bwIMG, 0, threshold);

        Imgproc.dilate(bwIMG, bwIMG, new Mat(), new Point(-1, 1), 1);

        List<MatOfPoint> contours = new ArrayList<MatOfPoint>();

        cIMG = bwIMG.clone();

        Imgproc.findContours(cIMG, contours, hovIMG, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);

        for (MatOfPoint cnt : contours) {

            MatOfPoint2f curve = new MatOfPoint2f(cnt.toArray());

            Imgproc.approxPolyDP(curve, approxCurve, 0.02 * Imgproc.arcLength(curve, true), true);

            int numberVertices = (int) approxCurve.total();

            double contourArea = Imgproc.contourArea(cnt);

            if (Math.abs(contourArea) < 100) {

            //Rectangle detected
            if (numberVertices >= 4 && numberVertices <= 6) {

                List<Double> cos = new ArrayList<>();

                for (int j = 2; j < numberVertices + 1; j++) {
                    cos.add(angle(approxCurve.toArray()[j % numberVertices], approxCurve.toArray()[j - 2], approxCurve.toArray()[j - 1]));


                double mincos = cos.get(0);
                double maxcos = cos.get(cos.size() - 1);

                if (numberVertices == 4 && mincos >= -0.3 && maxcos <= 0.5) {
                    Rect r = Imgproc.boundingRect(cnt);

                    Log.v("Test 1",Integer.toString(image.width()));
                    Log.v("Test 2",Integer.toString(image.height()));

    return dst;

I want to see over the rectangles the image, but I keep looking at the same unmodified. I am getting only once the log "Empty!", so it should be reading correctly the image and storing it on my Mat. Also, on the other 2 Logs where I am writting the image number of rows and columns, I am getting a number bigger than 0. So...

Is that the right way of checking if the image is correctly loaded? Do you now why that code is not working? I also read about the function addWeighted, but I tried to resized the smaller image and it failed.

Thanks in advance!!

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Closed for the following reason the question is answered, right answer was accepted by sturkmen
close date 2020-10-06 11:10:21.673574


checking if the image is correctly loaded?

you could return it, instead of dst .

berak gravatar imageberak ( 2019-06-27 23:35:59 -0500 )edit

@berak Thanks! I didn't think about that, I feel dumb right now. Do you know if the procedure I am doing to copying the image onto the frame should be correct?

Luciano Ruiz Morales gravatar imageLuciano Ruiz Morales ( 2019-07-02 17:11:50 -0500 )edit