Hello,
I'm new to OpenCV and new to extracting info from images. I have implemented the line segment detector to operate on an image that I have skeletonized (edges do not work for my purposes, I need centers of objects). The skeleton image is 8 bit single channel with values of 0 or 255. I want to find the lines in this image but the line segment detector (and the Hough transform) are returning a HUGE number of lines when there are really not that many. Since both the LSD and Hough are failing in similar ways, I suspect the input skeletonized image is the problem. I'm uncertain how to remedy the problem however since it is a fairly simple image with mostly zeros in it.
Below is the code, I didn't include how I read in the images but you get the idea, I hope. the skeleton comes out exactly as I need, here is a pic.
Mat img8bit(ysize, xsize, CV_8U);
Mat imgthresh(ysize, xsize, CV_8U);
threshold(img8bit, imgthresh, 200, 255, CV_THRESH_BINARY);
//this creates a Mat for storing the skeleton and sets it to zero
Mat skel(img.size(), CV_8UC1, cv::Scalar(0));
//this Mat is for intermediate storage for computations
Mat temp;
//stores eroded image
Mat eroded;
Mat element = getStructuringElement(cv::MORPH_CROSS, cv::Size(3, 3));
Mat closing(ysize, xsize, CV_8U);
//there are some holes in the circles, try to fill them in
morphologyEx(imgthresh, closing, MORPH_CLOSE, element);
//get skeleton
bool done = false;
while (!done)
{
erode(closing, eroded, element);
dilate(eroded, temp, element); // temp = open(img)
subtract(closing, temp, temp);
bitwise_or(skel, temp, skel);
eroded.copyTo(closing);
done = (countNonZero(closing) == 0);
}
Ptr ls = createLineSegmentDetector(LSD_REFINE_STD);
vector lines_std;
// Detect the lines
ls->detect(skel, lines_std);
// Show found lines
Mat drawnLines(img8bit);
ls->drawSegments(drawnLines, lines_std);
imshow("Standard refinement", drawnLines);
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