How to detect and crop rectangle and apply transformation from an image? [closed]

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Hello all,

I am developing an application for detect driving license and capture image of driving license using surface view and detect driving license and crop from those it's four corner using OpenCV.

so right now i am using canny edge detection and find the edges but i am not able to crop the image because canny edge detection return black and white image i am crop my original license image from it's edges.

Please suggest any best solution.

public Bitmap findEdges(Bitmap img)
{

    Mat rgba = new Mat();
    Utils.bitmapToMat(img, rgba);


    Mat edges = new Mat(rgba.size(), CvType.CV_8UC1);
    Imgproc.cvtColor(rgba, edges, Imgproc.COLOR_RGB2GRAY, 4);
    Imgproc.Canny(edges, edges, 40, 40);

    Bitmap resultBitmap = Bitmap.createBitmap(edges.cols(), edges.rows(), Bitmap.Config.ARGB_8888);
    Utils.matToBitmap(edges, resultBitmap);

    Mat rgbMat = new Mat();
    Mat grayMat = new Mat();
    Mat cannyMat;
    Mat linesMat = new Mat();
    BitmapFactory.Options o = new BitmapFactory.Options();

    // define the destination image size: A4 - 200 PPI
    int w_a4 = 1654, h_a4 = 2339;

    // TODO: 29/08/2016  May need to check sample size https://developer.android.com/training/displaying-bitmaps/load-bitmap.html
    o.inSampleSize = 4;
    o.inDither = false;

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    resultBitmap.compress(Bitmap.CompressFormat.PNG, 75, baos);
    byte[] b = baos.toByteArray();


    resultBitmap = BitmapFactory.decodeByteArray(b, 0, b.length);

    int w = resultBitmap.getWidth();
    int h = resultBitmap.getHeight();
    int min_w = 800;
    double scale = Math.min(10.0, w * 1.0 / min_w);
    int w_proc = (int) (w * 1.0 / scale);
    int h_proc = (int) (h * 1.0 / scale);
    Bitmap srcBitmap = Bitmap.createScaledBitmap(resultBitmap, w_proc, h_proc, false);
    Bitmap grayBitmap = Bitmap.createBitmap(w_proc, h_proc, Bitmap.Config.RGB_565);
    Bitmap cannyBitmap = Bitmap.createBitmap(w_proc, h_proc, Bitmap.Config.RGB_565);
    Bitmap linesBitmap = Bitmap.createBitmap(w_proc, h_proc, Bitmap.Config.RGB_565);


    Utils.bitmapToMat(srcBitmap, rgbMat);//convert original bitmap to Mat, R G B.


    Imgproc.cvtColor(rgbMat, grayMat, Imgproc.COLOR_RGB2GRAY);//rgbMat to gray grayMat


    cannyMat = getCanny(grayMat);


    Imgproc.HoughLinesP(cannyMat, linesMat, 1, Math.PI / 180, w_proc / 12, w_proc / 12, 20);

    // Calculate horizontal lines and vertical lines
    Log.e("opencv", "lines.cols " + linesMat.cols() + " w_proc/3: " + w_proc / 3);
    Log.e("opencv", "lines.rows" + linesMat.rows() + " w_proc/3: " + w_proc / 3);

    List<EdgesLine> horizontals = new ArrayList<>();
    List<EdgesLine> verticals = new ArrayList<>();
    for (int x = 0; x < linesMat.rows(); x++) {
        double[] vec = linesMat.get(x, 0);
        double x1 = vec[0],
                y1 = vec[1],
                x2 = vec[2],
                y2 = vec[3];
        Point start = new Point(x1, y1);
        Point end = new Point(x2, y2);

        EdgesLine line = new EdgesLine(start, end);
        if (Math.abs(x1 - x2) > Math.abs(y1 - y2)) {
            horizontals.add(line);
        } else {
            verticals.add(line);
        }

        if (BuildConfig.DEBUG) {
        }
    }

    Log.e("HoughLines", "completed HoughLines");
    Log.e("HoughLines", "linesMat size: " + linesMat.size());
    Log.e("HoughLines", "linesBitmap size: " + Integer.toString(linesBitmap.getHeight()) + " x " + Integer.toString(linesBitmap.getWidth()));
    Log.e("Lines Detected", Integer.toString(linesMat.rows()));

    if (linesMat.rows() > 400) {
        Context context = getApplicationContext();
        int duration = Toast.LENGTH_SHORT;
        Toast toast = Toast.makeText(context, "Please use a cleaner background", duration);
        toast.show();
    }

    if (horizontals.size() < 2) {
        if (horizontals.size() == 0 || horizontals.get(0)._center.y > h_proc / 2) {
            horizontals.add(new EdgesLine(new ...