AffineTransformation.java

//$HeadURL: svn+ssh://aschmitz@wald.intevation.org/deegree/base/trunk/resources/eclipse/files_template.xml $
/*----------------------------------------------------------------------------
 This file is part of deegree, http://deegree.org/
 Copyright (C) 2001-2011 by:
 - Department of Geography, University of Bonn -
 and
 - lat/lon GmbH -

 This library is free software; you can redistribute it and/or modify it under
 the terms of the GNU Lesser General Public License as published by the Free
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 any later version.
 This library is distributed in the hope that it will be useful, but WITHOUT
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 details.
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 Contact information:

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 Aennchenstr. 19, 53177 Bonn
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 http://lat-lon.de/

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package org.deegree.igeo.modules.georef;

import georegression.fitting.affine.MotionAffinePoint2D_F64;
import georegression.struct.affine.Affine2D_F64;
import georegression.struct.point.Point2D_F64;
import georegression.transform.affine.AffinePointOps;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.deegree.igeo.modules.georef.ControlPointModel.Point;

/**
 * 
 * @author <a href="mailto:schmitz@lat-lon.de">Andreas Schmitz</a>
 * @author last edited by: $Author: stranger $
 * 
 * @version $Revision: $, $Date: $
 */
public class AffineTransformation {

    /**
     * @param points
     * @return a transformation from right to left (the inverse)
     */
    public static double[] approximate( List<Point> points ) {
        int n = points.size() - 1;
        if ( n < 3 ) {
            return null;
        }

        List<Point2D_F64> list1 = new ArrayList<Point2D_F64>( n );
        List<Point2D_F64> list2 = new ArrayList<Point2D_F64>( n );
        Iterator<Point> iter = points.iterator();
        for ( int i = 0; i < n; ++i ) {
            Point p = iter.next();
            if ( p.x0 == null || p.y0 == null || p.x1 == null || p.y1 == null ) {
                continue;
            }
            Point2D_F64 p1 = new Point2D_F64( p.x0, p.y0 );
            Point2D_F64 p2 = new Point2D_F64( p.x1, p.y1 );
            list1.add( p1 );
            list2.add( p2 );
        }

        MotionAffinePoint2D_F64 m = new MotionAffinePoint2D_F64();
        m.process( list1, list2 );
        Affine2D_F64 t = m.getMotion();

        // calculate residuals
        Iterator<Point2D_F64> iter1 = list1.iterator();
        Iterator<Point2D_F64> iter2 = list2.iterator();
        iter = points.iterator();

        while ( iter1.hasNext() ) {
            Point p = iter.next();
            Point2D_F64 p1 = iter1.next();
            Point2D_F64 p2 = iter2.next();
            Point2D_F64 newp = AffinePointOps.transform( t, p1, null );
            p.resx = p2.x - newp.x;
            p.resy = p2.y - newp.y;
        }

        // give back inverse transformation
        t = new Affine2D_F64( 1, 0, 0, -1, 0, 0 ).concat( t.invert( null ), null );

        return new double[] { t.a11, t.a12, t.a21, t.a22, t.tx, t.ty };
    }

}