DericheGradientImage.H

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/*---------------------------------------------------------------------+
 | Library QgarLib, graphics analysis and recognition                  |
 | Copyright (C) 2002  Qgar Project, LORIA                             |
 |                                                                     |
 | This library is free software; you can redistribute it and/or       |
 | modify it under the terms of the GNU Lesser General Public          |
 | License version 2.1, as published by the Free Software Foundation.  |
 |                                                                     |
 | This library is distributed in the hope that it will be useful,     |
 | but WITHOUT ANY WARRANTY; without even the implied warranty of      |
 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                |
 | See the GNU Lesser General Public License for more details.         |
 |                                                                     |
 | The GNU Lesser General Public License is included in the file       |
 | LICENSE.LGPL, in the root directory of the Qgar packaging. See      |
 | http://www.gnu.org/licenses/lgpl.html for the terms of the licence. |
 | To receive a paper copy, write to the Free Software Foundation,     |
 | Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.       |
 |                                                                     |
 | Contact Project Qgar for any information:                           |
 |   LORIA - équipe Qgar                                               |
 |   B.P. 239, 54506 Vandoeuvre-lès-Nancy Cedex, France                |
 |   email: qgar-contact@loria.fr                                      |
 |   http://www.qgar.org/                                              |
 *---------------------------------------------------------------------*/


#ifndef __DERICHEGRADIENTIMAGE_H_INCLUDED__
#define __DERICHEGRADIENTIMAGE_H_INCLUDED__


/**
 * @file     DericheGradientImage.H
 * @brief    Header file of class qgar::DericheGradientImage.
 *
 * @author   <a href="mailto:qgar-develop@loria.fr?subject=Qgar fwd Karl Tombre">Karl Tombre</a>
 * @date     July 3,  2001  11:15
 * @since    Qgar 1.0
 */

// For RCS/CVS use: Do not delete
/* $Id: DericheGradientImage.H,v 1.13 2005/10/14 17:05:45 masini Exp $ */


// QGAR
#include <qgarlib/AbstractGradientImage.H>
#include <qgarlib/GenImage.H>


namespace qgar
{


/**
 * @class DericheGradientImage DericheGradientImage.H "qgarlib/DericheGradientImage.H"
 * @ingroup IMGPROC_GRAD
 * @brief Deriche's optimal edge detector.
 *
 * The code is based on a previous implementation by Djemel Ziou
 * and Salvatore Tabbone, as described in
 * [<a href="Bibliography.html#Deriche-1987">Deriche,&nbsp;1987</a>].
 * 
 * @author   <a href="mailto:qgar-develop@loria.fr?subject=Qgar fwd Karl Tombre">Karl Tombre</a>
 * @date     July 3,  2001  11:15
 * @since    Qgar 1.0
 */
class DericheGradientImage

  : public AbstractGradientImage

{
// -------------------------------------------------------------------
// P U B L I C    M E M B E R S
// -------------------------------------------------------------------
public:

  /** @name Constructors */
  //        ============
  //@{
  /**
   * @brief Construct from given grey-level image.
   * @param img          grey-level image to derive
   * @param alpha        parameter of the Deriche filter (default <b>1.0</b>)
   * @param w            parameter of the Deriche filter (default <b>0.01</b>)
   * @param normalized   = <b>1</b> if filter is normalized to have a
   *   surface of 1. Default is <b>0</b>: In this case, the filter
   *   preserves the height of the step edge.
   */
  DericheGradientImage(const GreyLevelImage& img,
                       float alpha = 1.0,
                       float w = .01,
                       int normalized = 0);

  /**
   * @brief Construct from a float image.
   *
   * @param img          float image to derive
   * @param alpha        parameter of the Deriche filter (default <b>1.0</b>)
   * @param w            parameter of the Deriche filter (default <b>0.01</b>)
   * @param normalized   = <b>1</b> if filter is normalized to have a
   *   surface of 1. Default is <b>0</b>: In this case, the filter
   *   preserves the height of the step edge.
   */
  DericheGradientImage(const FloatImage& img,
                       float alpha = 1.0,
                       float w = .01,
                       int normalized = 0);

  //@}

// -------------------------------------------------------------------
// P R O T E C T E D   M E M B E R S
// -------------------------------------------------------------------
protected:

  /** @name Parameters (see Deriche's paper) */
  //        ================================
  //@{
  /**
   * @brief The alpha parameter.
   */
  float _alpha;

  /**
   * @brief The w parameter.
   */
  float _w;
  //@}

// -------------------------------------------------------------------
// P R I V A T E    M E M B E R S
// -------------------------------------------------------------------
private:

  /** @name Parameters to implement the IIR filter */
  //        ======================================
  //@{
  ///
  float a;
  ///
  float a0;
  ///
  float a1;
  ///
  float a2;
  ///
  float a3;
  ///
  float b1;
  ///
  float b2;
  //@}


  /** @name Filtering */
  //        =========
  //@{
  /**
   * @brief X filter.
   */
  void dfilterX();

  /**
   * Y filter.
   */
  void dfilterY();
  //@}


  /** @name Auxiliaries */
  //        ===========
  //@{
  /**
   * @brief The effective computation of the contour image.
   */
  void PRIVATEbuildDericheImage(int normalized);
  //@}

// -------------------------------------------------------------------
}; // class DericheGradientImage


} // namespace qgar


#endif /* __DERICHEGRADIENTIMAGE_H_INCLUDED__ */