Detect and extend white lines in an image.

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Hello,

I have an image with white lines in it and I just need a program to extend those white lines C:\fakepath\vlcsnap.png Please guest me what should I do.

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int thresh = 100;
Mat dst, cdst;
Mat img, original;

Mat whiteFilter(const Mat& src)
{
    assert(src.type() == CV_8UC3);

    Mat whiteOnly;
    inRange(src, Scalar(150, 150, 150), Scalar(255, 255, 255), whiteOnly);

    return whiteOnly;
}

void on_trackbar(int, void*)
{//This function gets called whenever a
    // trackbar position is changed

    Mat whiteOnly = whiteFilter(original);
    img = original.clone();

    Canny(whiteOnly, dst, 50, 200, 3);
    cvtColor(dst, cdst, CV_GRAY2BGR);

    vector<Vec2f> lines;
    HoughLines(dst, lines, 1, CV_PI / 180, thresh, 0, 0);

    for (size_t i = 0; i < lines.size(); i++)
    {
        float rho = lines[i][0], theta = lines[i][1];
        Point pt1, pt2;
        double a = cos(theta), b = sin(theta);
        double x0 = a*rho, y0 = b*rho;
        pt1.x = cvRound(x0 + 1000 * (-b));
        pt1.y = cvRound(y0 + 1000 * (a));
        pt2.x = cvRound(x0 - 1000 * (-b));
        pt2.y = cvRound(y0 - 1000 * (a));
        line(img, pt1, pt2, Scalar(255, 255, 255), 1, CV_AA);
    }

    imshow("detected lines", img);

}

int main(int argc, char** argv)
{
    Mat input = imread("D:/Pictures/vlcsnap.png");
    if (input.empty())
    {
        cout << "File not found" << endl;
        return 0;
    }

    img = input.clone();
    original = input.clone();

    imshow("input", input);

    Mat whiteOnly = whiteFilter(input);

    imshow("whiteOnly", whiteOnly);

    Canny(whiteOnly, dst, 50, 200, 3);
    cvtColor(dst, cdst, CV_GRAY2BGR);

    imshow("detected lines", img);

    createTrackbar("thresh", "detected lines", &thresh, 200, on_trackbar);
    waitKey();

    return 0;
}

The result I'm getting is not what i desire please help me.

Result C:\fakepath\white.png C:\fakepath\detected.png