/// <summary>
/// Tries to find the composite pattern and returns the output parameter image_points.
/// In case of success the boolean value 'true' is returned.
/// Note, that CompositePatterns can only be found, if the cameras' intrinsics are set.
///
/// The algorithm is working as follows:
/// If the main pattern 'patternA' could be found, the algorithm is finished already and the resulting
/// image_points are known and returned.
/// If only 'patternB' could be found, the given object_points of 'patternA' are transformed in the
/// 'patternB' coordinate system, using the predefined transformation matrix.
/// Furthermore, an extrinsic calibration is performed in order to find the extrinsic matrix, which describes
/// the relation between camera coordinate system and the coordinate system of 'patternB'.
/// Finally, the library function 'ProjectPoints' is called in order to project the transformed object_points
/// (currently expressed in 'patternB'-coordinates) into the camera image plane.
/// The projected points correspond to the image_points of 'patternA'.
/// ==> To sum up: the predefined transformation is used to calculate the image_points of 'patternA', even
/// if 'patternA' is invisible.
/// </summary>
/// <param name="img"> Input grayscale image. </param>
/// <param name="image_points"> 2D output image points. </param>
/// <returns> true... if pattern has been found; false... otherwise. </returns>
public override bool FindPattern(Emgu.CV.Image <Emgu.CV.Structure.Gray, byte> img, out System.Drawing.PointF[] image_points)
{
if (this.IntrinsicParameters != null && _patternA != null && _patternB != null)
{
bool foundA = false;
System.Drawing.PointF[] currentImagePointsA;
System.Drawing.PointF[] currentImagePointsB;
//set the object_points of the composite pattern to the object_points of 'patternA'
this.ObjectPoints = _patternA.ObjectPoints;
//try to find 'patternA'
foundA = _patternA.FindPattern(img, out currentImagePointsA);
//if 'patternA' could be found: the image_points have been found.
if (foundA)
{
image_points = currentImagePointsA;
//_logger.Info("Pattern found.");
return(true);
}
else
//else: try to find 'patternB'
if (_patternB.FindPattern(img, out currentImagePointsB))
{
ExtrinsicCalibration ec_B = null;
Emgu.CV.ExtrinsicCameraParameters ecp_B = null;
Matrix extrinsic_matrix = Matrix.Identity(4, 4);
Matrix temp_matrix = null;
Emgu.CV.Structure.MCvPoint3D32f[] transformedCornerPoints = new Emgu.CV.Structure.MCvPoint3D32f[_patternA.ObjectPoints.Length];
try
{
//if 'patternB' has been found: find the extrinsic matrix (relation between coordinate systems of 'patternB' and camera
ec_B = new ExtrinsicCalibration(_patternB.ObjectPoints, this.IntrinsicParameters);
ecp_B = ec_B.Calibrate(currentImagePointsB);
if (ecp_B != null)
{
//form the resulting extrinsic matrix to a homogeneous (4x4) matrix.
temp_matrix = Parsley.Core.Extensions.ConvertToParsley.ToParsley(ecp_B.ExtrinsicMatrix);
extrinsic_matrix.SetMatrix(0, temp_matrix.RowCount - 1, 0, temp_matrix.ColumnCount - 1, temp_matrix);
//transform object points of A into B coordinate system.
transformedCornerPoints = MatrixTransformation.TransformVectorToEmgu(_transformationBToA.Inverse(), 1.0, _patternA.ObjectPoints).ToArray <Emgu.CV.Structure.MCvPoint3D32f>();
//project the points into the 2D camera plane (image_points)
image_points = Emgu.CV.CameraCalibration.ProjectPoints(transformedCornerPoints, ecp_B, this.IntrinsicParameters);
return(true);
}
else
{
_logger.Warn("Error calculating extrinsic parameters.");
image_points = null;
return(false);
}
}
catch (Exception e)
{
_logger.Warn("Caught Exception: {0}.", e);
image_points = null;
return(false);
}
}
else
{
//reset the image_points if the pattern could not be found.
image_points = null;
return(false);
}
}
else
{
_logger.Warn("Error: Intrinsics are needed to find a Composite Pattern but not available.");
image_points = null;
return(false);
}
}
