Java Code Examples for org.opencv.imgproc.Imgproc#Sobel

void Sobel() {
    Mat grayMat = new Mat();
    Mat sobel = new Mat(); //Mat to store the final result

    //Matrices to store gradient and absolute gradient respectively
    Mat grad_x = new Mat();
    Mat abs_grad_x = new Mat();

    Mat grad_y = new Mat();
    Mat abs_grad_y = new Mat();

    //Converting the image to grayscale
    Imgproc.cvtColor(originalMat, grayMat, Imgproc.COLOR_BGR2GRAY);

    //Calculating gradient in horizontal direction
    Imgproc.Sobel(grayMat, grad_x, CvType.CV_16S, 1, 0, 3, 1, 0);

    //Calculating gradient in vertical direction
    Imgproc.Sobel(grayMat, grad_y, CvType.CV_16S, 0, 1, 3, 1, 0);

    //Calculating absolute value of gradients in both the direction
    Core.convertScaleAbs(grad_x, abs_grad_x);
    Core.convertScaleAbs(grad_y, abs_grad_y);

    //Calculating the resultant gradient
    Core.addWeighted(abs_grad_x, 0.5, abs_grad_y, 0.5, 1, sobel);

    //Converting Mat back to Bitmap
    Utils.matToBitmap(sobel, currentBitmap);
    imageView.setImageBitmap(currentBitmap);
}
 

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {
    mRgba = inputFrame.rgba();
    mGray = inputFrame.gray();

    switch (MainActivity.viewMode) {
        case MainActivity.VIEW_MODE_RGBA:
            return mRgba;

        case MainActivity.VIEW_MODE_HIST:
            return mRgba;

        case MainActivity.VIEW_MODE_CANNY:
            Imgproc.Canny(mGray, mIntermediateMat, 80, 100);
            Imgproc.cvtColor(mIntermediateMat, mGray, Imgproc.COLOR_GRAY2BGRA, 4);
            return mGray;

        case MainActivity.VIEW_MODE_SOBEL:
            Imgproc.Sobel(mGray, mGray, CvType.CV_8U, 1, 1);
            //			Core.convertScaleAbs(mIntermediateMat, mIntermediateMat, 10, 0);
            Imgproc.cvtColor(mGray, mGray, Imgproc.COLOR_GRAY2BGRA, 4);
            return mGray;

        case MainActivity.VIEW_MODE_PIXELIZE:
            Imgproc.resize(mGray, mIntermediateMat, mSize0, 0.1, 0.1,
                Imgproc.INTER_NEAREST);
            Imgproc.resize(mIntermediateMat, mRgba, mRgba.size(), 0.0, 0.0,
                Imgproc.INTER_NEAREST);
            return mRgba;

        case MainActivity.VIEW_MODE_GRAY:
            return mGray;

        case MainActivity.VIEW_MODE_FEATURES:
            FindFeatures(mGray.getNativeObjAddr(), mRgba.getNativeObjAddr());
            return mRgba;

        default:
            return mRgba;
    }
}
 

public static Rect detectBorder(Mat original){
    Mat src = original.clone();
    Log.d(TAG, "1 original: " + src.toString());

    Imgproc.GaussianBlur(src, src, new Size(3, 3), 0);
    Log.d(TAG, "2.1 --> Gaussian blur done\n blur: " + src.toString());

    Imgproc.cvtColor(src, src, Imgproc.COLOR_RGBA2GRAY);
    Log.d(TAG, "2.2 --> Grayscaling done\n gray: " + src.toString());

    Mat sobelX = new Mat();
    Mat sobelY = new Mat();

    Imgproc.Sobel(src, sobelX, CvType.CV_32FC1, 2, 0, 5, 1, 0);
    Log.d(TAG, "3.1 --> Sobel done.\n X: " + sobelX.toString());
    Imgproc.Sobel(src, sobelY, CvType.CV_32FC1, 0, 2, 5, 1, 0);
    Log.d(TAG, "3.2 --> Sobel done.\n Y: " + sobelY.toString());

    Mat sum_img = new Mat();
    Core.addWeighted(sobelX, 0.5, sobelY, 0.5, 0.5, sum_img);
    //Core.add(sobelX, sobelY, sum_img);
    Log.d(TAG, "4 --> Addition done. sum: " + sum_img.toString());

    sobelX.release();
    sobelY.release();

    Mat gray = new Mat();
    Core.normalize(sum_img, gray, 0, 255, Core.NORM_MINMAX, CvType.CV_8UC1);
    Log.d(TAG, "5 --> Normalization done. gray: " + gray.toString());
    sum_img.release();

    Mat row_proj = new Mat();
    Mat col_proj = new Mat();
    Core.reduce(gray, row_proj, 1, Core.REDUCE_AVG, CvType.CV_8UC1);
    Log.d(TAG, "6.1 --> Reduce done. row: " + row_proj.toString());

    Core.reduce(gray, col_proj, 0, Core.REDUCE_AVG, CvType.CV_8UC1);
    Log.d(TAG, "6.2 --> Reduce done. col: " + col_proj.toString());
    gray.release();

    Imgproc.Sobel(row_proj, row_proj, CvType.CV_8UC1, 0, 2);
    Log.d(TAG, "7.1 --> Sobel done. row: " + row_proj.toString());

    Imgproc.Sobel(col_proj, col_proj, CvType.CV_8UC1, 2, 0);
    Log.d(TAG, "7.2 --> Sobel done. col: " + col_proj.toString());

    Rect result = new Rect();

    int half_pos = (int) (row_proj.total()/2);
    Mat row_sub = new Mat(row_proj, new Range(0, half_pos), new Range(0, 1));
    Log.d(TAG, "8.1 --> Copy sub matrix done. row: " + row_sub.toString());
    result.y = (int) Core.minMaxLoc(row_sub).maxLoc.y;
    Log.d(TAG, "8.2 --> Minmax done. Y: " + result.y);
    row_sub.release();
    Mat row_sub2 = new Mat(row_proj, new Range(half_pos, (int) row_proj.total()), new Range(0, 1));
    Log.d(TAG, "8.3 --> Copy sub matrix done. row: " + row_sub2.toString());
    result.height = (int) (Core.minMaxLoc(row_sub2).maxLoc.y + half_pos - result.y);
    Log.d(TAG, "8.4 --> Minmax done. Height: " + result.height);
    row_sub2.release();

    half_pos = (int) (col_proj.total()/2);
    Mat col_sub = new Mat(col_proj, new Range(0, 1), new Range(0, half_pos));
    Log.d(TAG, "9.1 --> Copy sub matrix done. col: " + col_sub.toString());
    result.x = (int) Core.minMaxLoc(col_sub).maxLoc.x;
    Log.d(TAG, "9.2 --> Minmax done. X: " + result.x);
    col_sub.release();
    Mat col_sub2 = new Mat(col_proj, new Range(0, 1), new Range(half_pos, (int) col_proj.total()));
    Log.d(TAG, "9.3 --> Copy sub matrix done. col: " + col_sub2.toString());
    result.width = (int) (Core.minMaxLoc(col_sub2).maxLoc.x + half_pos - result.x);
    Log.d(TAG, "9.4 --> Minmax done. Width: " + result.width);
    col_sub2.release();

    row_proj.release();
    col_proj.release();
    src.release();

    return result;
}
 

public static List<MatOfPoint> findContoursForMRZ(Mat src){
    Mat img = src.clone();
    src.release();
    double ratio = getScaleRatio(img.size());
    int width = (int) (img.size().width / ratio);
    int height = (int) (img.size().height / ratio);
    Size newSize = new Size(width, height);
    Mat resizedImg = new Mat(newSize, CvType.CV_8UC4);
    Imgproc.resize(img, resizedImg, newSize);

    Mat gray = new Mat();
    Imgproc.cvtColor(resizedImg, gray, Imgproc.COLOR_BGR2GRAY);
    Imgproc.medianBlur(gray, gray, 3);
    //Imgproc.blur(gray, gray, new Size(3, 3));

    Mat morph = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(13, 5));
    Mat dilatedImg = new Mat();
    Imgproc.morphologyEx(gray, dilatedImg, Imgproc.MORPH_BLACKHAT, morph);
    gray.release();

    Mat gradX = new Mat();
    Imgproc.Sobel(dilatedImg, gradX, CvType.CV_32F, 1, 0);
    dilatedImg.release();
    Core.convertScaleAbs(gradX, gradX, 1, 0);
    Core.MinMaxLocResult minMax = Core.minMaxLoc(gradX);
    Core.convertScaleAbs(gradX, gradX, (255/(minMax.maxVal - minMax.minVal)),
            - ((minMax.minVal * 255) / (minMax.maxVal - minMax.minVal)));
    Imgproc.morphologyEx(gradX, gradX, Imgproc.MORPH_CLOSE, morph);

    Mat thresh = new Mat();
    Imgproc.threshold(gradX, thresh, 0, 255, Imgproc.THRESH_OTSU);
    gradX.release();
    morph.release();

    morph = Imgproc.getStructuringElement(Imgproc.MORPH_RECT, new Size(21, 21));
    Imgproc.morphologyEx(thresh, thresh, Imgproc.MORPH_CLOSE, morph);
    Imgproc.erode(thresh, thresh, new Mat(), new Point(-1, -1), 4);
    morph.release();

    int col = (int) resizedImg.size().width;
    int p = (int) (resizedImg.size().width * 0.05);
    int row = (int) resizedImg.size().height;
    for(int i = 0; i < row; i++)
    {
        for(int j = 0; j < p; j++){
            thresh.put(i, j, 0);
            thresh.put(i, col-j, 0);
        }
    }

    List<MatOfPoint> contours = new ArrayList<>();
    Mat hierarchy = new Mat();
    Imgproc.findContours(thresh, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
    hierarchy.release();

    Log.d(TAG, "contours found: " + contours.size());

    Collections.sort(contours, new Comparator<MatOfPoint>() {
        @Override
        public int compare(MatOfPoint o1, MatOfPoint o2) {
            return Double.valueOf(Imgproc.contourArea(o2)).compareTo(Imgproc.contourArea(o1));
        }
    });

    return contours;
}