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public void removeBorder( String filePath ) { Mat grayImage = Imgcodecs.imread( filePath, Imgcodecs.IMREAD_GRAYSCALE ); Mat thresholdInverted = new Mat(); Imgproc.threshold( grayImage, thresholdInverted, 127.0, 255.0, Imgproc.THRESH_BINARY_INV + Imgproc.THRESH_OTSU ); Imgcodecs.imwrite( "C:\abc1.png", thresholdInverted );

    List<MatOfPoint> horizontalContours = morphOpenAndFindContours( thresholdInverted, new Size( 5, 1 ));


    List<MatOfPoint> verticalContours = morphOpenAndFindContours( thresholdInverted, new Size( 1, 10 ));

    this.drawWhiteContours( verticalContours, grayImage );
    this.drawWhiteContours( horizontalContours, grayImage );
    Imgcodecs.imwrite( "C:\\result.jpg", grayImage );
}
private void drawWhiteContours( List<MatOfPoint> contours, Mat image )
{
    for ( int i = 0; i < contours.size(); i++ ) {
        Imgproc.drawContours( image, contours, i, new Scalar( 255 ), -1 );
    }
}
private List<MatOfPoint> morphOpenAndFindContours( Mat img, Size kSize)
{
    Mat kernel = Imgproc.getStructuringElement( Imgproc.MORPH_RECT, kSize );

    Mat openedImage = new Mat();
    Imgproc.morphologyEx( img, openedImage, Imgproc.MORPH_OPEN, kernel, new Point( -1, -1 ), 1 );
    Mat dilateKernel = Imgproc.getStructuringElement( Imgproc.MORPH_RECT, new Size( 5, 5 ) );

    Imgproc.dilate( openedImage, openedImage, dilateKernel );

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

    Imgproc.findContours( openedImage, contours, new Mat(), Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE );

    return contours;
}