/// <summary>
/// Initialize frame grabber with camera
/// </summary>
/// <param name="camera"></param>
public FrameGrabber(Camera camera) {
_camera = camera;
_lock_event = new object();
_fts = new FixedTimeStep(30);
_bw = new BackgroundWorker();
_bw.WorkerSupportsCancellation = true;
_bw.DoWork += new DoWorkEventHandler(_bw_DoWork);
_bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(_bw_RunWorkerCompleted);
_stopped = new ManualResetEvent(false);
}
/// <summary>
/// Creates a off-axis perspective matrix from camera intrinsics.
/// </summary>
/// <remarks> Note that OSG layouts their matrices in row-major order, so you
/// need to transpose this matrix, before passing it to OSG</remarks>
/// <param name="camera">Camera with intrinsic parameters</param>
/// <returns>Perspective matrix in column-major</returns>
public static Matrix FromCamera(Camera camera, double near, double far) {
if (!camera.HasIntrinsics) {
throw new ArgumentException("Camera has no intrinsic calibration");
}
// see
// http://opencv.willowgarage.com/wiki/Posit
// http://opencv.willowgarage.com/documentation/camera_calibration_and_3d_reconstruction.html
// http://aoeu.snth.net/static/gen-perspective.pdf
// http://www.hitl.washington.edu/artoolkit/mail-archive/message-thread-00654-Re--Questions-concering-.html
Matrix m = new Matrix(4, 4, 0.0);
Emgu.CV.IntrinsicCameraParameters icp = camera.Intrinsics;
double fx = icp.IntrinsicMatrix[0, 0];
double fy = icp.IntrinsicMatrix[1, 1];
double px = icp.IntrinsicMatrix[0, 2];
double py = icp.IntrinsicMatrix[1, 2];
double w = camera.FrameWidth;
double h = camera.FrameHeight;
double dist = far - near;
// First row
m[0, 0] = 2.0 * (fx / w);
m[0, 2] = 2.0 * (px / w) - 1.0;
// Second row
m[1, 1] = 2.0 * (fy / h);
m[1, 2] = 2.0 * (py / h) - 1.0;
// Third row
m[2, 2] = -(far + near) / dist;
m[2, 3] = -2.0 * far * near / dist;
// Fourth row (note the flip)
m[3, 2] = -1.0;
return m;
}
/// <summary>
/// Calculates the transformation matrix, which is used to transform the 3d-object points, which were scanned with reference
/// to the moved marker coordinate system, back to the initial marker system and henceforth back to the camera system.
/// The camera object is needed in order to gain the current camera frame. Furthermore, the cameras' intrinsics are needed
/// to perform an extrinsic calibration. Note, that every kind of pattern can be used.
///
/// The transformation matrix is calculated as follows:
/// * If 'UpdateTransformation' is being called for the first time, an extrinsic calibration is performed in order to find
/// the initial orientation of the used pattern.
/// * If the initial orientation has already been found, the extrinsic calibration is performed again. Afterwards
/// the current orientation is available, represented by the extrinsic matrix.
/// * Form the extrinsic matrix (4x3) (current position) to a homogeneous 4x4 matrix.
/// * The final transformation matrix is calculated as follows: _final = initial * current.Inverse();
/// </summary>
public bool UpdateTransformation(Camera the_cam)
{
Matrix extrinsicM1 = Matrix.Identity(4, 4);
ExtrinsicCameraParameters ecp_pattern = null;
ExtrinsicCalibration ec_pattern = null;
Emgu.CV.Image<Gray, Byte> gray_img = null;
System.Drawing.PointF[] currentImagePoints;
//first call: calculate extrinsics for initial position
if (_firstCallUpdateTransformation == true && _cpattern != null)
{
gray_img = the_cam.Frame().Convert<Gray, Byte>();
//set the patterns property: intrinsic parameters
_cpattern.IntrinsicParameters = the_cam.Intrinsics;
if (_cpattern.FindPattern(gray_img, out currentImagePoints))
{
try
{
//extr. calibration (initial position)
ec_pattern = new ExtrinsicCalibration(_cpattern.ObjectPoints, the_cam.Intrinsics);
ecp_pattern = ec_pattern.Calibrate(currentImagePoints);
if (ecp_pattern != null)
{
_ecp_A = ecp_pattern;
_extrinsicMatrix_A = ExtractExctrinsicMatrix(_ecp_A);
_logger.Info("Initial Position found.");
_firstCallUpdateTransformation = false;
}
}
catch (Exception e)
{
_logger.Warn("Initial Position - Caught Exception: {0}.", e);
_firstCallUpdateTransformation = true;
_ecp_A = null;
return false;
}
}
else
{
_logger.Warn("Pattern not found.");
_firstCallUpdateTransformation = true;
_ecp_A = null;
return false;
}
}
//if initial position and pattern are available - calculate the transformation
if (_ecp_A != null && _cpattern != null)
{
gray_img = the_cam.Frame().Convert<Gray, Byte>();
//try to find composite pattern
if (_cpattern.FindPattern(gray_img, out currentImagePoints))
{
//extrinsic calibration in order to find the current orientation
ec_pattern = new ExtrinsicCalibration(_cpattern.ObjectPoints, the_cam.Intrinsics);
ecp_pattern = ec_pattern.Calibrate(currentImagePoints);
if (ecp_pattern != null)
{
//extract current extrinsic matrix
extrinsicM1 = ExtractExctrinsicMatrix(ecp_pattern);
_logger.Info("UpdateTransformation: Transformation found.");
}
else
{
_logger.Warn("UpdateTransformation: Extrinsics of moved marker system not found.");
return false;
}
}
else
{
_logger.Warn("UpdateTransformation: Pattern not found.");
return false;
}
//now calculate the final transformation matrix
_final = _extrinsicMatrix_A * extrinsicM1.Inverse();
return true;
}
else
{
_logger.Warn("UpdateTransformation: No Pattern has been chosen.");
return false;
}
}