LSD algoritm

    Once considering detect a line from image, Hough Line Detection algorithm must be the first choice, it's classic and easily to understand, but in this blog I would like to share another useful algorithm: Line Segment Detection, it's faster and more accurate than Hough, here is a small example about LSD for reference:http://download.csdn.net/download/cutelily2014/10034091

    Next is the script to perform LSD's magic, lsd.cpp.

    Reference from: http://blog.csdn.net/mollylee1011/article/details/47292783

/*
This is a simple example to display LSD algorithm in Line Detection
Notes: It read image flow from a video named video.mp4.
*/
#include <iostream>
#include <string>
#include "opencv2/core.hpp"
#include "opencv2/core/utility.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui/highgui.hpp"
using namespace std;
using namespace cv;
int main(int argc, char **argv)
{
    // Step 1: read image and convert the origin color image to a binary
    VideoCapture capture(argv[1]);
    Mat image;
    namedWindow("video", WINDOW_NORMAL);
    if(!capture.isOpened())
        throw "Error: Reading video failed !";
    while(capture.read(image))
    {
        Mat img_hsv(image);
        cvtColor(image, img_hsv, CV_BGR2HSV);
        //lower red mask
        Mat mask0;
        inRange(img_hsv, Scalar(0, 50, 50), Scalar(10, 255, 255), mask0);
        //upper red mask
        Mat mask1;
        inRange(img_hsv, Scalar(100, 50, 50), Scalar(180, 255, 255), mask1);
        Mat img_filt = mask0 + mask1;
        //imshow("video", img_filt);

        // Step 2: detect line by LSD algorithm
        Canny(image, image, 50, 200, 3);
        Ptr<LineSegmentDetector> ls = createLineSegmentDetector(LSD_REFINE_STD);
        //Ptr<LineSegmentDetector> ls = createLineSegmentDetector(LSD_REFINE_NONE);

        double start = double(getTickCount());
        vector<Vec4f> lines_std;
        ls->detect(img_filt, lines_std);

        // Step 3: display detected lines
        double duration_ms = (double(getTickCount()) - start) * 1000 / getTickFrequency();
        std::cout << "It took " << duration_ms << " ms." << std::endl;
        //Mat drawnLines(image);
        ls->drawSegments(image, lines_std);
        imshow("video", image);
        waitKey(20);
    }
    waitKey();
    return 0;
}