/**
* Fit a circle to three given points on the circumference. The method draws lines (chords)
* between two pairs of the points, constructs their perpendicular bisectors, and finds the
* intersection point of those two lines. This is the centre of the circle as radii passing
* through the centre are perpendicular bisectors of chords in a circle. The radius is the
* distance between the centre and any one of the initial three points.
*/
private QDCircle threePointCircleFit(List <QDPoint> pts)
{
QDLine l1 = new QDLine(pts[0], pts[1]);
QDLine l2 = new QDLine(pts[1], pts[2]);
QDInfiniteLine i1 = new QDInfiniteLine(l1.getMidpoint(), l1.getPerpAngleD());
QDInfiniteLine i2 = new QDInfiniteLine(l2.getMidpoint(), l2.getPerpAngleD());
QDPoint centre = i1.intersect(i2);
float radius = QDUtils.QDUtils.getPtToPtDist(centre, pts[0]);
return(new QDCircle(centre, radius));
}
public void getIntrinsicConstraints(QDInputPointSet ptSet)
{
if (ptSet.shapeType == QDShapeTypes.LINE)
{
QDLine line = (QDLine)ptSet.initialFit;
float angle = line.angleD;
// Check for vertical line and adjust by midpoint pivot
if ((90.0f - line_snap_thresh < angle && angle < 90.0f + line_snap_thresh) ||
(-90.0f - line_snap_thresh < angle && angle < -90.0f + line_snap_thresh) && !line.vertical)
{
QDPoint newStart, newFinish;
if (line.start.y > line.getMidpoint().y)
{
newStart = new QDPoint(line.midPoint.x, line.midPoint.y + (0.5f * line.length));
newFinish = new QDPoint(line.midPoint.x, line.midPoint.y - (0.5f * line.length));
}
else
{
newStart = new QDPoint(line.midPoint.x, line.midPoint.y - (0.5f * line.length));
newFinish = new QDPoint(line.midPoint.x, line.midPoint.y + (0.5f * line.length));
}
ptSet.fittedShape = new QDLine(newStart, newFinish);
ptSet.constraints.Add(QDConstraintTypes.VERTICAL_LINE);
}
// Check for horizontal line and adjust by midpoint pivot
else if ((-line_snap_thresh < angle && angle < line_snap_thresh) ||
(180.0f - line_snap_thresh < angle || angle < -180.0f + line_snap_thresh))
{
float length = (float)Math.Sqrt(Math.Pow(line.start.x - line.finish.x, 2.0f) + Math.Pow(line.start.y - line.finish.y, 2.0f));
QDPoint midPt = new QDPoint((line.start.x + line.finish.x) * 0.5f, (line.start.y + line.finish.y) * 0.5f);
QDPoint newStart = new QDPoint();
QDPoint newFinish = new QDPoint();
newStart.y = newFinish.y = midPt.y;
if (line.start.x > midPt.x)
{
newStart.x = midPt.x + (0.5f * length);
newFinish.x = midPt.x - (0.5f * length);
}
else
{
newStart.x = midPt.x - (0.5f * length);
newFinish.x = midPt.x + (0.5f * length);
}
ptSet.fittedShape = new QDLine(newStart, newFinish);
ptSet.constraints.Add(QDConstraintTypes.HORIZONTAL_LINE);
}
}
}