CppEllipse CppEllipse::fromMatrix(const tmv::Matrix<double>& m, Angle& rotation, bool& parityFlip)
{
dbg<<"ellipse from matrix "<<m<<'\n';
assert(m.nrows()==2 && m.ncols()==2);
double det = m(0,0)*m(1,1) - m(0,1)*m(1,0);
parityFlip = false;
double scale;
if (det < 0) {
parityFlip = true;
scale = -det;
} else if (det==0.) {
// Degenerate transformation. Return some junk
return CppEllipse(CppShear(0.0, 0.0), -std::numeric_limits<double>::max());
} else {
scale = det;
}
// Determine and remove the dilation
double mu = 0.5*std::log(scale);
// Now make m m^T matrix, which is symmetric
// a & b are diagonal elements here
double a = m(0,1)*m(0,1) + m(0,0)*m(0,0);
double b = m(1,1)*m(1,1) + m(1,0)*m(1,0);
double c = m(1,1)*m(0,1) + m(1,0)*m(0,0);
double eta = acosh(std::max(1.,0.5*(a+b)/scale));
Angle beta = 0.5*std::atan2(2.*c, a-b) * radians;
CppShear s;
s.setEtaBeta(eta,beta);
s.getMatrix(a,b,c);
// Now look for the rotation
rotation = std::atan2(-c*m(0,0)+a*m(1,0), b*m(0,0)-c*m(1,0)) * radians;
return CppEllipse(s,mu, Position<double>(0.,0.));
}
static void wrap() {
static char const * doc =
"SBTransform is an affine transformation of another SBProfile.\n"
"Origin of original shape will now appear at x0.\n"
"Flux is NOT conserved in transformation - SB is preserved."
;
bp::class_< SBTransform, bp::bases<SBProfile> >("SBTransform", doc, bp::no_init)
.def(bp::init<const SBProfile &, double, double, double, double,
Position<double>, double >(
(bp::args("sbin", "mA", "mB", "mC", "mD"),
bp::arg("x0")=Position<double>(0.,0.),
bp::arg("fluxScaling")=1.)
))
.def(bp::init<const SBProfile &, const CppEllipse &, double>(
(bp::arg("sbin"), bp::arg("e")=CppEllipse(), bp::arg("fluxScaling")=1.)
))
.def(bp::init<const SBTransform &>())
;
}
// CppEllipses share the ordering conventions: e1 + e2 is transform
// e1 followed by transform e2. Transform objects, not coords.
CppEllipse CppEllipse::operator-() const
{
Position<double> x3(-x0);
x3 /= expmu;
return CppEllipse(-s, -mu, s.inv(x3));
}
