/// <summary>
/// Takes a circle in image space and returns a cooresponding ellipse in image space.
/// This is an ill posed problem. The center is respected but the radius could be taken
/// anywhere around the circle in image space, and that yields different radii in world space.
/// We use the point along the X axis as the radius.
/// </summary>
public Ellipse GetEllipseFromCircle(PointF center, float radius, out PointF radiusLeftInImage, out PointF radiusRightInImage)
{
radiusLeftInImage = new PointF(center.X - radius, center.Y);
radiusRightInImage = new PointF(center.X + radius, center.Y);
if (calibratorType == CalibratorType.Line)
{
return(new Ellipse(center, radius, radius, 0));
}
// Rebuild the world-space circle based on center and radius alone.
PointF centerInWorld = GetPoint(center);
// Estimate the radius in world space.
// Get scalar will assumes reference direction to be X-axis in image space.
float radiusInWorld = GetScalar(radius);
// Get the intersection points of a horizontal diameter.
// This is used to draw a line from the center to the outline of the ellipse in perspective.
radiusLeftInImage = GetImagePoint(centerInWorld.Translate(-radiusInWorld, 0));
radiusRightInImage = GetImagePoint(centerInWorld.Translate(radiusInWorld, 0));
// Get the square enclosing the circle for mapping.
PointF a = GetImagePoint(centerInWorld.Translate(-radiusInWorld, -radiusInWorld));
PointF b = GetImagePoint(centerInWorld.Translate(radiusInWorld, -radiusInWorld));
PointF c = GetImagePoint(centerInWorld.Translate(radiusInWorld, radiusInWorld));
PointF d = GetImagePoint(centerInWorld.Translate(-radiusInWorld, radiusInWorld));
QuadrilateralF quadImage = new QuadrilateralF(a, b, c, d);
ProjectiveMapping mapping = new ProjectiveMapping();
mapping.Update(QuadrilateralF.CenteredUnitSquare, quadImage);
return(mapping.Ellipse());
}
/// <summary>
/// Takes a circle in real world coordinates and returns a cooresponding ellipse in image coordinates.
/// </summary>
public Ellipse GetEllipseFromCircle(PointF center, float radius)
{
if (calibratorType == CalibratorType.Line)
{
return(new Ellipse(GetImagePoint(center), GetImageScalar(radius), GetImageScalar(radius), 0));
}
// Get the square enclosing the circle for mapping.
PointF a = GetImagePoint(center.Translate(-radius, -radius));
PointF b = GetImagePoint(center.Translate(radius, -radius));
PointF c = GetImagePoint(center.Translate(radius, radius));
PointF d = GetImagePoint(center.Translate(-radius, radius));
QuadrilateralF quadImage = new QuadrilateralF(a, b, c, d);
ProjectiveMapping mapping = new ProjectiveMapping();
mapping.Update(QuadrilateralF.CenteredUnitSquare, quadImage);
return(mapping.Ellipse());
}