/// <summary>
/// Calculate horizontal offset of the vertical line (center) in the binary image
/// </summary>
/// <param name="src"> binary image </param>
/// <returns> horizontal offset of the vertical line </returns>
private int CenterOfLine(Mat src)
{
// sobel in X-direction
//Image<Gray, float> sobel = src.Clone().Erode(3).Sobel(1, 0, 3);
Mat sobel = new Mat(src.Size(), src.Type());
Imgproc.Erode(src, sobel, Imgproc.GetStructuringElement(Imgproc.MorphRect, new Size(3, 3)));
//Imgproc.Sobel(src, sobel, src.Type(), 0, 3);
// min max loc
double min = 0, max = 0;
Core.Core.MinMaxLocResult result = Core.Core.MinMaxLoc(sobel);// MinMaxLoc(sobel, ref min, ref max, ref minLoc, ref maxLoc);
// invalid state
if (result.MinLoc.X <= result.MaxLoc.X)
{
return(src.Width() / 2);
}
return(((int)(result.MinLoc.X) - (int)(result.MaxLoc.X)) / 2 + (int)(result.MaxLoc.X));
}
/// <summary>
/// Run a sliding window algorithm on the bird eye view to find the 2 sides of the lane.
/// </summary>
/// <param name="birdEye">bird eye image</param>
/// <param name="res"> result of windowing </param>
/// <param name="windows"> number of stacked windows </param>
public void FitLinesInSlidingWindows(Mat birdEye, out Mat res, int windows)
{
LeftPoints = new List <Point>();
RightPoints = new List <Point>();
// erode by 2x2 kernel
Imgproc.Erode(birdEye, birdEye, Imgproc.GetStructuringElement(Imgproc.MorphRect, new Size(2, 2)));
// alloc res have the same size and type as bird eye
res = new Mat(birdEye.Size(), birdEye.Type());
// convert to BGR for result drawing
Imgproc.CvtColor(birdEye, res, Imgproc.ColorGray2bgr);
// crop half bottom of bird eye
Mat cropped = new Mat(birdEye, new Rect(0, birdEye.Height() / 2, birdEye.Width(), birdEye.Height() / 2));
// find left and right starting point
int left, right;
SlidingWindowsStartLoc(cropped, out left, out right);
// current window locations
int currentWindowLeft = left;
int currentWindowRight = right;
// window settings & buffer
int margin = 100;
int minpix = 140;
int winHeight = birdEye.Height() / windows;
// calculate windows
for (int i = 0; i < windows; i++)
{
// calculate window size and location
int winYhigh = birdEye.Height() - i * winHeight;
int winXleftLow = currentWindowLeft - margin;
int winXrightLow = currentWindowRight - margin;
Rect leftRect = new Rect(winXleftLow, winYhigh - winHeight, margin * 2, winHeight);
Rect rightRect = new Rect(winXrightLow, winYhigh - winHeight, margin * 2, winHeight);
Imgproc.Rectangle(res, new Point(leftRect.X, leftRect.Y), new Point(leftRect.X + leftRect.Width, leftRect.Y + leftRect.Height), new Scalar(20, 20, 255), 3);
Imgproc.Rectangle(res, new Point(rightRect.X, rightRect.Y), new Point(rightRect.X + rightRect.Width, rightRect.Y + rightRect.Height), new Scalar(20, 20, 255), 3);
int goodLeft;
int goodRight;
// save position
LeftPoints.Add(new Point(winXleftLow + margin, winYhigh - (winHeight / 2)));
RightPoints.Add(new Point(winXrightLow + margin, winYhigh - (winHeight / 2)));
Mat birdEyeROI;
birdEyeROI = birdEye.Submat(leftRect);
goodLeft = Core.Core.CountNonZero(birdEyeROI);
birdEyeROI = birdEye.Submat(rightRect);
goodRight = Core.Core.CountNonZero(birdEyeROI);
if (goodLeft > minpix)
{
// recenter
birdEyeROI = birdEye.Submat(leftRect);
currentWindowLeft = CenterOfLine(birdEyeROI) + leftRect.X;
}
if (goodRight > minpix)
{
// recenter
birdEyeROI = birdEye.Submat(rightRect);
currentWindowRight = CenterOfLine(birdEyeROI) + rightRect.X;
}
}
// Draw midpoints
foreach (Point p in LeftPoints)
{
//res.Draw(new Rectangle(new Point((int)p.X, (int)p.Y), new Size(20, 20)), new Bgr(50, 50, 230), 12);
Imgproc.Rectangle(res, new Point((int)p.X, (int)p.Y), new Point(p.X + 20, p.Y + 20), new Scalar(50, 50, 230), 12);
}
foreach (Point p in RightPoints)
{
//res.Draw(new Rectangle(new Point((int)p.X, (int)p.Y), new Size(20, 20)), new Bgr(50, 50, 230), 12);
Imgproc.Rectangle(res, new Point((int)p.X, (int)p.Y), new Point(p.X + 20, p.Y + 20), new Scalar(50, 50, 230), 12);
}
BirdEye = res;
}