static public CvPoint[] DistillContours(
CvMat inputMat_grey, int maxContourPoints, CvPoint offset,
ContourRetrieval retr = ContourRetrieval.External, ContourChain chain = ContourChain.ApproxSimple)
{
// maxContourPoints (original name "maxContours"); 5 or 100??!!!
// TODO : The CV docs specifically state that the image should be in binary format. Check if it is.
//std::vector<std::vector<cv::Point>> updateContours;
//std::vector<cv::Vec4i> m_hierarchy; // TODO : Not used currently, but determine if it's gonna be needed for points-tracking
// see usage here: http://stackoverflow.com/questions/35418714/opencvsharps-findcontour-returns-wrong-data
ContourData contoursData = Filters.FindContours(inputMat_grey, retr, chain, offset);
CvPoint[][] contoursFound = contoursData.contours; // original name: "updateContours"
if (contoursFound.Length == 0)
{
return(null); // TODO : cannot process frame, no contours found. Maybe it's time to rethink about that strategy and not simply
}
// return empty handed!!!
double[] contourAreas = contoursData.areas;
Point[] newPtV;
// find index of max-area contour
int index = 0;
double maxArea = 0;
for (int i = contourAreas.Length - 1; i >= 0; --i)
{
double area = contourAreas[i];
if (area > maxArea)
{
index = i;
maxArea = area;
}
}
// approximate contour down to 4 points
// TODO : This idea sounds weird. Why not check all contours and find one that is best approximated by 4 points???
CvPoint[] biggestContour = contoursFound[index];
newPtV = new Point[biggestContour.Length];
PointOps.CopyCvPointsToPoints(biggestContour, newPtV); //PointOps.CopyCvPointsToGenericPointsArray( biggestContour, newPtV );
double epsilon = 1;
while (newPtV.Length > maxContourPoints)
{
newPtV = Cv2.ApproxPolyDP(newPtV, epsilon++, true);
// TODO : Is incrementing epsilon by 1 a bit stupid? Maybe increment exponentially?
}
// finally
CvPoint[] cvPoints = new CvPoint[newPtV.Length];
PointOps.CopyPointsToCvPoints(newPtV, cvPoints);
return(cvPoints);
}
// The OpenCVSharp is for some reason complicated and needs to be abstracted. So here is the abstraction layer...
// TODO : The CV docs specifically state that the image should be in binary format. Check if it is.
// see usage here: http://stackoverflow.com/questions/35418714/opencvsharps-findcontour-returns-wrong-data
static public ContourData FindContours(CvMat input, ContourRetrieval retrievalMode, ContourChain chainMode, CvPoint offset, double minArea = 0)
{
List <CvPoint[]> pointsArrays = new List <CvPoint[]>();
List <double> areas = new List <double>();
CvSeq <CvPoint> contoursRaw;
using (CvMemStorage storage = new CvMemStorage())
{
Cv.FindContours(input, storage, out contoursRaw, CvContour.SizeOf, retrievalMode, chainMode, offset);
using (CvContourScanner scanner = new CvContourScanner(input, storage, CvContour.SizeOf, retrievalMode, chainMode, offset))
{
foreach (CvSeq <CvPoint> c in scanner)
{
List <CvPoint> points = new List <CvPoint>();
//Some contours have negative area!
double area = c.ContourArea();
if (Math.Abs(area) >= minArea)
{
areas.Add(area);
foreach (CvPoint p in c.ToArray())
{
points.Add(p);
}
pointsArrays.Add(points.ToArray());
}
}
}
}
ContourData data = new ContourData();
data.contours = pointsArrays.ToArray();
data.areas = areas.ToArray();
return(data);
}