Transform2D.h

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// 
//   Copyright (C) 2003-2006 Rational Discovery LLC
//
//   @@ All Rights Reserved  @@
//
#ifndef __RD_TRANSFORM2D_H__
#define __RD_TRANSFORM2D_H__

#include "Transform.h"
#include <Numerics/SquareMatrix.h>

namespace RDGeom {
  class Point2D;
  const unsigned int DIM_2D=3;

  class Transform2D : public RDNumeric::SquareMatrix<double> {
  public:
    //! \brief Constructor
    /*!  
      Initialize to an identity matrix transformation
      This is a 3x3 matrix that includes the rotation and translation parts
      see Foley's "Introduction to Computer Graphics" for the representation

      Operator *= and = are provided by the parent class square matrix. 
      Operator *= needs some explanation, since the order matters. This transform gets set to
      the combination other and the current state of this transform
      If this_old and this_new are the states of this object before and after this function
      we have
              this_new(point) = this_old(other(point))
    */
    Transform2D() : RDNumeric::SquareMatrix<double>(DIM_2D,0.0) {
      unsigned int i, id;
      for (i = 0; i < DIM_2D; i++) {
        id = i*(DIM_2D+1);
        d_data[id] = 1.0;
      }
    }

    void setToIdentity();

    void TransformPoint(Point2D &pt) const;

    void SetTranslation(const Point2D &pt);
 
    /*! \brief Set the tranform so that the specified points are aligned
     *
     * The resulting tranformation will align pt1 with ref1, and rotation
     * pt2 such that the line betweem (pt1, pt2) will align with 
     * with the line (ref1, ref2)
     */
    void SetTransform(const Point2D &ref1, const Point2D &ref2,
                      const Point2D &pt1, const Point2D &pt2);

    /*! \brief Set the trans form to counterclock wise rotation by the specified value around point
     *
     * ARGUMENTS:
     *   - pt : point about which to rotate
     *   - angle : the angle byt which to rotate
     */
    void SetTransform(const Point2D &pt, double angle);

  private:
        
  };
}

/*! \brief Combine two transforms and return the results as a new transform
 *
 * The order is important here, on two transforms t1 and t2
 * t3 = t1*t2 
 * The resulting transform t3 has the folliwng effect
 *  t3(point) = t1(t2(point))
 */
RDGeom::Transform2D operator* (const RDGeom::Transform2D &t1, const RDGeom::Transform2D &t2);


#endif