GPXSee/src/map/transform.cpp

#include "projection.h"
#include "matrix.h"
#include "transform.h"

void Transform::simple(const QList<ReferencePoint> &points)
{
	if (points.at(0).xy.x() == points.at(1).xy.x()
	  || points.at(0).xy.y() == points.at(1).xy.y()) {
		_errorString = "Invalid reference points tuple";
		return;
	}

	qreal sX, sY, dX, dY;
	sX = (points.at(0).xy.x() - points.at(1).xy.x())
	  / (points.at(0).pp.x() - points.at(1).pp.x());
	sY = (points.at(1).xy.y() - points.at(0).xy.y())
	  / (points.at(1).pp.y() - points.at(0).pp.y());
	dX = points.at(1).xy.x() - points.at(1).pp.x() * sX;
	dY = points.at(0).xy.y() - points.at(0).pp.y() * sY;

	_transform = QTransform(sX, 0, 0, sY, dX, dY);
}

void Transform::affine(const QList<ReferencePoint> &points)
{
	Matrix c(3, 2);
	c.zeroize();
	for (size_t i = 0; i < c.h(); i++) {
		for (size_t j = 0; j < c.w(); j++) {
			for (int k = 0; k < points.size(); k++) {
				double f[3], t[2];

				f[0] = points.at(k).pp.x();
				f[1] = points.at(k).pp.y();
				f[2] = 1.0;
				t[0] = points.at(k).xy.x();
				t[1] = points.at(k).xy.y();
				c.m(i,j) += f[i] * t[j];
			}
		}
	}

	Matrix Q(3, 3);
	Q.zeroize();
	for (int qi = 0; qi < points.size(); qi++) {
		double v[3];

		v[0] = points.at(qi).pp.x();
		v[1] = points.at(qi).pp.y();
		v[2] = 1.0;
		for (size_t i = 0; i < Q.h(); i++)
			for (size_t j = 0; j < Q.w(); j++)
				Q.m(i,j) += v[i] * v[j];
	}

	Matrix M = Q.augemented(c);
	if (!M.eliminate()) {
		_errorString = "Singular transformation matrix";
		return;
	}

	_transform = QTransform(M.m(0,3), M.m(0,4), M.m(1,3), M.m(1,4), M.m(2,3),
	  M.m(2,4));
}

Transform::Transform(const QList<ReferencePoint> &points)
{
	if (points.count() < 2)
		_errorString = "Insufficient number of reference points";
	else if (points.size() == 2)
		simple(points);
	else
		affine(points);
}

QDebug operator<<(QDebug dbg, const ReferencePoint &p)
{
	dbg.nospace() << "ReferencePoint(" << p.xy << ", " << p.pp << ")";
	return dbg.maybeSpace();
}