// Get optimized quadrilateral area
private List <IntPoint> GetShapeCorners(List <IntPoint> edgePoints)
{
return(shapeOptimizer.OptimizeShape(PointsCloud.FindQuadrilateralCorners(edgePoints)));
}
/// <summary>
/// Check if a shape specified by the set of points fits a convex polygon
/// specified by the set of corners.
/// </summary>
///
/// <param name="edgePoints">Shape's points to check.</param>
/// <param name="corners">Corners of convex polygon to check fitting into.</param>
///
/// <returns>Returns <see langword="true"/> if the specified shape fits
/// the specified convex polygon or <see langword="false"/> otherwise.</returns>
///
/// <remarks><para>The method checks if the set of specified points form the same shape
/// as the set of provided corners.</para></remarks>
///
public bool CheckIfPointsFitShape(List <IntPoint> edgePoints, List <IntPoint> corners)
{
int cornersCount = corners.Count;
// lines coefficients (for representation as y(x)=k*x+b)
float[] k = new float[cornersCount];
float[] b = new float[cornersCount];
float[] div = new float[cornersCount]; // precalculated divisor
bool[] isVert = new bool[cornersCount];
for (int i = 0; i < cornersCount; i++)
{
IntPoint currentPoint = corners[i];
IntPoint nextPoint = (i + 1 == cornersCount) ? corners[0] : corners[i + 1];
if (!(isVert[i] = nextPoint.X == currentPoint.X))
{
k[i] = (float)(nextPoint.Y - currentPoint.Y) / (nextPoint.X - currentPoint.X);
b[i] = currentPoint.Y - k[i] * currentPoint.X;
div[i] = (float)Math.Sqrt(k[i] * k[i] + 1);
}
}
// calculate distances between edge points and polygon sides
float meanDistance = 0;
for (int i = 0, n = edgePoints.Count; i < n; i++)
{
float minDistance = float.MaxValue;
for (int j = 0; j < cornersCount; j++)
{
float distance = 0;
if (!isVert[j])
{
distance = (float)Math.Abs((k[j] * edgePoints[i].X + b[j] - edgePoints[i].Y) / div[j]);
}
else
{
distance = Math.Abs(edgePoints[i].X - corners[j].X);
}
if (distance < minDistance)
{
minDistance = distance;
}
}
meanDistance += minDistance;
}
meanDistance /= edgePoints.Count;
// get bounding rectangle of the corners list
IntPoint minXY, maxXY;
PointsCloud.GetBoundingRectangle(corners, out minXY, out maxXY);
IntPoint rectSize = maxXY - minXY;
float maxDitance = Math.Max(minAcceptableDistortion,
((float)rectSize.X + rectSize.Y) / 2 * relativeDistortionLimit);
return(meanDistance <= maxDitance);
}
/// <summary>
/// Find corners of quadrilateral or triangular area, which contains the specified collection of points.
/// </summary>
///
/// <param name="cloud">Collection of points to search quadrilateral for.</param>
///
/// <returns>Returns a list of 3 or 4 points, which are corners of the quadrilateral or
/// triangular area filled by specified collection of point. The first point in the list
/// is the point with lowest X coordinate (and with lowest Y if there are several points
/// with the same X value). The corners are provided in counter clockwise order
/// (<a href="http://en.wikipedia.org/wiki/Cartesian_coordinate_system">Cartesian
/// coordinate system</a>).</returns>
///
/// <remarks><para>The method makes an assumption that the specified collection of points
/// form some sort of quadrilateral/triangular area. With this assumption it tries to find corners
/// of the area.</para>
///
/// <para><note>The method does not search for <b>bounding</b> quadrilateral/triangular area,
/// where all specified points are <b>inside</b> of the found quadrilateral/triangle. Some of the
/// specified points potentially may be outside of the found quadrilateral/triangle, since the
/// method takes corners only from the specified collection of points, but does not calculate such
/// to form true bounding quadrilateral/triangle.</note></para>
///
/// <para>See <see cref="QuadrilateralRelativeDistortionLimit"/> property for additional information.</para>
/// </remarks>
///
public static List <IntPoint> FindQuadrilateralCorners(IEnumerable <IntPoint> cloud)
{
// quadrilateral's corners
List <IntPoint> corners = new List <IntPoint>( );
// get bounding rectangle of the points list
IntPoint minXY, maxXY;
PointsCloud.GetBoundingRectangle(cloud, out minXY, out maxXY);
// get cloud's size
IntPoint cloudSize = maxXY - minXY;
// calculate center point
IntPoint center = minXY + cloudSize / 2;
// acceptable deviation limit
float distortionLimit = quadrilateralRelativeDistortionLimit * (cloudSize.X + cloudSize.Y) / 2;
// get the furthest point from (0,0)
IntPoint point1 = PointsCloud.GetFurthestPoint(cloud, center);
// get the furthest point from the first point
IntPoint point2 = PointsCloud.GetFurthestPoint(cloud, point1);
corners.Add(point1);
corners.Add(point2);
// get two furthest points from line
IntPoint point3, point4;
float distance3, distance4;
PointsCloud.GetFurthestPointsFromLine(cloud, point1, point2,
out point3, out distance3, out point4, out distance4);
// ideally points 1 and 2 form a diagonal of the
// quadrilateral area, and points 3 and 4 form another diagonal
// but if one of the points (3 or 4) is very close to the line
// connecting points 1 and 2, then it is one the same line ...
// which means corner was not found.
// in this case we deal with a trapezoid or triangle, where
// (1-2) line is one of it sides.
// another interesting case is when both points (3) and (4) are
// very close the (1-2) line. in this case we may have just a flat
// quadrilateral.
if (
((distance3 >= distortionLimit) && (distance4 >= distortionLimit)) ||
((distance3 < distortionLimit) && (distance3 != 0) &&
(distance4 < distortionLimit) && (distance4 != 0)))
{
// don't add one of the corners, if the point is already in the corners list
// (this may happen when both #3 and #4 points are very close to the line
// connecting #1 and #2)
if (!corners.Contains(point3))
{
corners.Add(point3);
}
if (!corners.Contains(point4))
{
corners.Add(point4);
}
}
else
{
// it seems that we deal with kind of trapezoid,
// where point 1 and 2 are on the same edge
IntPoint tempPoint = (distance3 > distance4) ? point3 : point4;
// try to find 3rd point
PointsCloud.GetFurthestPointsFromLine(cloud, point1, tempPoint,
out point3, out distance3, out point4, out distance4);
bool thirdPointIsFound = false;
if ((distance3 >= distortionLimit) && (distance4 >= distortionLimit))
{
if (point4.DistanceTo(point2) > point3.DistanceTo(point2))
{
point3 = point4;
}
thirdPointIsFound = true;
}
else
{
PointsCloud.GetFurthestPointsFromLine(cloud, point2, tempPoint,
out point3, out distance3, out point4, out distance4);
if ((distance3 >= distortionLimit) && (distance4 >= distortionLimit))
{
if (point4.DistanceTo(point1) > point3.DistanceTo(point1))
{
point3 = point4;
}
thirdPointIsFound = true;
}
}
if (!thirdPointIsFound)
{
// failed to find 3rd edge point, which is away enough from the temp point.
// this means that the clound looks more like triangle
corners.Add(tempPoint);
}
else
{
corners.Add(point3);
// try to find 4th point
float tempDistance;
PointsCloud.GetFurthestPointsFromLine(cloud, point1, point3,
out tempPoint, out tempDistance, out point4, out distance4);
if ((distance4 >= distortionLimit) && (tempDistance >= distortionLimit))
{
if (tempPoint.DistanceTo(point2) > point4.DistanceTo(point2))
{
point4 = tempPoint;
}
}
else
{
PointsCloud.GetFurthestPointsFromLine(cloud, point2, point3,
out tempPoint, out tempDistance, out point4, out distance4);
if ((tempPoint.DistanceTo(point1) > point4.DistanceTo(point1)) &&
(tempPoint != point2) && (tempPoint != point3))
{
point4 = tempPoint;
}
}
if ((point4 != point1) && (point4 != point2) && (point4 != point3))
{
corners.Add(point4);
}
}
}
// put the point with lowest X as the first
for (int i = 1, n = corners.Count; i < n; i++)
{
if ((corners[i].X < corners[0].X) ||
((corners[i].X == corners[0].X) && (corners[i].Y < corners[0].Y)))
{
IntPoint temp = corners[i];
corners[i] = corners[0];
corners[0] = temp;
}
}
// sort other points in counter clockwise order
float k1 = (corners[1].X != corners[0].X) ?
((float)(corners[1].Y - corners[0].Y) / (corners[1].X - corners[0].X)) :
((corners[1].Y > corners[0].Y) ? float.PositiveInfinity : float.NegativeInfinity);
float k2 = (corners[2].X != corners[0].X) ?
((float)(corners[2].Y - corners[0].Y) / (corners[2].X - corners[0].X)) :
((corners[2].Y > corners[0].Y) ? float.PositiveInfinity : float.NegativeInfinity);
if (k2 < k1)
{
IntPoint temp = corners[1];
corners[1] = corners[2];
corners[2] = temp;
float tk = k1;
k1 = k2;
k2 = tk;
}
if (corners.Count == 4)
{
float k3 = (corners[3].X != corners[0].X) ?
((float)(corners[3].Y - corners[0].Y) / (corners[3].X - corners[0].X)) :
((corners[3].Y > corners[0].Y) ? float.PositiveInfinity : float.NegativeInfinity);
if (k3 < k1)
{
IntPoint temp = corners[1];
corners[1] = corners[3];
corners[3] = temp;
float tk = k1;
k1 = k3;
k3 = tk;
}
if (k3 < k2)
{
IntPoint temp = corners[2];
corners[2] = corners[3];
corners[3] = temp;
float tk = k2;
k2 = k3;
k3 = tk;
}
}
return(corners);
}
/// <summary>
/// Check sub type of a convex polygon.
/// </summary>
///
/// <param name="corners">Corners of the convex polygon to check.</param>
///
/// <returns>Return detected sub type of the specified shape.</returns>
///
/// <remarks><para>The method check corners of a convex polygon detecting
/// its subtype. Polygon's corners are usually retrieved using <see cref="IsConvexPolygon"/>
/// method, but can be any list of 3-4 points (only sub types of triangles and
/// quadrilateral are checked).</para>
///
/// <para>See <see cref="AngleError"/> and <see cref="LengthError"/> properties,
/// which set acceptable errors for polygon sub type checking.</para>
/// </remarks>
///
public PolygonSubType CheckPolygonSubType(List <IntPoint> corners)
{
PolygonSubType subType = PolygonSubType.Unknown;
// get bounding rectangle of the points list
IntPoint minXY, maxXY;
PointsCloud.GetBoundingRectangle(corners, out minXY, out maxXY);
// get cloud's size
IntPoint cloudSize = maxXY - minXY;
float maxLengthDiff = lengthError * (cloudSize.X + cloudSize.Y) / 2;
if (corners.Count == 3)
{
// get angles of the triangle
float angle1 = GeometryTools.GetAngleBetweenVectors(corners[0], corners[1], corners[2]);
float angle2 = GeometryTools.GetAngleBetweenVectors(corners[1], corners[2], corners[0]);
float angle3 = GeometryTools.GetAngleBetweenVectors(corners[2], corners[0], corners[1]);
// check for equilateral triangle
if ((Math.Abs(angle1 - 60) <= angleError) &&
(Math.Abs(angle2 - 60) <= angleError) &&
(Math.Abs(angle3 - 60) <= angleError))
{
subType = PolygonSubType.EquilateralTriangle;
}
else
{
// check for isosceles triangle
if ((Math.Abs(angle1 - angle2) <= angleError) ||
(Math.Abs(angle2 - angle3) <= angleError) ||
(Math.Abs(angle3 - angle1) <= angleError))
{
subType = PolygonSubType.IsoscelesTriangle;
}
// check for rectangled triangle
if ((Math.Abs(angle1 - 90) <= angleError) ||
(Math.Abs(angle2 - 90) <= angleError) ||
(Math.Abs(angle3 - 90) <= angleError))
{
subType = (subType == PolygonSubType.IsoscelesTriangle) ?
PolygonSubType.RectangledIsoscelesTriangle : PolygonSubType.RectangledTriangle;
}
}
}
else if (corners.Count == 4)
{
// get angles between 2 pairs of opposite sides
float angleBetween1stPair = GeometryTools.GetAngleBetweenLines(corners[0], corners[1], corners[2], corners[3]);
float angleBetween2ndPair = GeometryTools.GetAngleBetweenLines(corners[1], corners[2], corners[3], corners[0]);
// check 1st pair for parallelism
if (angleBetween1stPair <= angleError)
{
subType = PolygonSubType.Trapezoid;
// check 2nd pair for parallelism
if (angleBetween2ndPair <= angleError)
{
subType = PolygonSubType.Parallelogram;
// check angle between adjacent sides
if (Math.Abs(GeometryTools.GetAngleBetweenVectors(corners[1], corners[0], corners[2]) - 90) <= angleError)
{
subType = PolygonSubType.Rectangle;
}
// get length of 2 adjacent sides
float side1Length = (float)corners[0].DistanceTo(corners[1]);
float side2Length = (float)corners[0].DistanceTo(corners[3]);
if (Math.Abs(side1Length - side2Length) <= maxLengthDiff)
{
subType = (subType == PolygonSubType.Parallelogram) ?
PolygonSubType.Rhombus : PolygonSubType.Square;
}
}
}
else
{
// check 2nd pair for parallelism - last chence to detect trapezoid
if (angleBetween2ndPair <= angleError)
{
subType = PolygonSubType.Trapezoid;
}
}
}
return(subType);
}
/// <summary>
/// Optimize specified shape.
/// </summary>
///
/// <param name="shape">Shape to be optimized.</param>
///
/// <returns>Returns final optimized shape, which may have reduced amount of points.</returns>
///
public List <IntPoint> OptimizeShape(List <IntPoint> shape)
{
// optimized shape
List <IntPoint> optimizedShape = new List <IntPoint>( );
// list of recently removed points
List <IntPoint> recentlyRemovedPoints = new List <IntPoint>( );
if (shape.Count <= 3)
{
// do nothing if shape has 3 points or less
optimizedShape.AddRange(shape);
}
else
{
float distance = 0;
// add first 2 points to the new shape
optimizedShape.Add(shape[0]);
optimizedShape.Add(shape[1]);
int pointsInOptimizedHull = 2;
for (int i = 2, n = shape.Count; i < n; i++)
{
// add new point
optimizedShape.Add(shape[i]);
pointsInOptimizedHull++;
// add new candidate for removing to the list
recentlyRemovedPoints.Add(optimizedShape[pointsInOptimizedHull - 2]);
// calculate maximum distance between new candidate line and recently removed point
PointsCloud.GetFurthestPointFromLine(recentlyRemovedPoints,
optimizedShape[pointsInOptimizedHull - 3], optimizedShape[pointsInOptimizedHull - 1],
out distance);
if ((distance <= maxDistanceToRemove) &&
((pointsInOptimizedHull > 3) || (i < n - 1)))
{
optimizedShape.RemoveAt(pointsInOptimizedHull - 2);
pointsInOptimizedHull--;
}
else
{
// don't need to remove the last candidate point
recentlyRemovedPoints.Clear( );
}
}
if (pointsInOptimizedHull > 3)
{
// check the last point
recentlyRemovedPoints.Add(optimizedShape[pointsInOptimizedHull - 1]);
PointsCloud.GetFurthestPointFromLine(recentlyRemovedPoints,
optimizedShape[pointsInOptimizedHull - 2], optimizedShape[0],
out distance);
if (distance <= maxDistanceToRemove)
{
optimizedShape.RemoveAt(pointsInOptimizedHull - 1);
pointsInOptimizedHull--;
}
else
{
recentlyRemovedPoints.Clear( );
}
if (pointsInOptimizedHull > 3)
{
// check the first point
recentlyRemovedPoints.Add(optimizedShape[0]);
PointsCloud.GetFurthestPointFromLine(recentlyRemovedPoints,
optimizedShape[pointsInOptimizedHull - 1], optimizedShape[1],
out distance);
if (distance <= maxDistanceToRemove)
{
optimizedShape.RemoveAt(0);
}
}
}
}
return(optimizedShape);
}
