cvrMergeHSIToImage.h

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/*
 * Copyright (C) 1998-2006
 * Lehrstuhl fuer Technische Informatik, RWTH-Aachen, Germany
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/**
 * \file   cvrMergeHSIToImage.h
 * \author Pablo Alvarado
 * \author Stefan Syberichs
 * \author Thomas Rusert
 * \date   19.04.99
 *
 * $Id: cvrMergeHSIToImage.h,v 1.3 2006/01/06 05:02:10 alvarado Exp $
 */

#ifndef _CVR_MERGE_HSI_TO_IMAGE_H_
#define _CVR_MERGE_HSI_TO_IMAGE_H_

#include "cvrMergeImage.h"

namespace cvr {

  /**
   * Merge HSI (Hue Saturation Intensity) channels.
   *
   * It is assumed that all channels have "valid" values, i.e., if the inputs
   * are of type cvr::channel, the Hue has values between 0.0 and 1.0 (meaning
   * 0 to 360 degrees), Saturation and Intensity between 0.0 and 1.0.  For
   * cvr::channel8, the possible value ranges are always valid.
   *
   * If any component is not valid, then unpredictible results have to be
   * expected, including segmentation faults, as the computations use some LUT
   * to improve speed.
   *
   * The transformation from HSI to RGB depends on the value range of hue (H).
   * It first computes chromaticity values r,g,b:
   *
   * If \f$0^\circ \leq H < 120^\circ\f$
   *
   * \f[
   *   \begin{aligned}
   *     r &= \frac{1}{3}\left[1+\frac{S \cos(H)}{\cos(60^\circ-H)}\right] \\
   *     g &= 1-(r+b) \\
   *     b &= \frac{1}{3}(1-S)
   *   \end{aligned}
   * \f]
   *
   * If \f$120^\circ \leq H < 240^\circ\f$
   *
   * \f[
   *   \begin{aligned}
   *     r &= \frac{1}{3}(1-S) \\
   *     g &= \frac{1}{3}\left[1+\frac{S \cos(H-120^\circ)}
   *                                  {\cos(180^\circ-H)}\right] \\
   *     b &= 1-(r+g)
   *   \end{aligned}
   * \f]
   *
   * If \f$240^\circ \leq H < 360^\circ\f$
   *
   * \f[
   *   \begin{aligned}
   *     g &= \frac{1}{3}(1-S) \\
   *     b &= \frac{1}{3}\left[1+\frac{S \cos(H-240^\circ)}
   *                                  {\cos(300^\circ-H)}\right] \\
   *     r &= 1-(g+b)
   *   \end{aligned}
   * \f]
   *
   * With these chromaticity values, the RGB tuple can easily be computed as
   *
   * \f[ \begin{aligned} R &= 3rI \\ G &= 3gI \\ B &= 3bI \\ \end{aligned} \f]
   *
   * @see cvr::splitImageToHSI
   *
   * @ingroup gColor
   */
  class mergeHSIToImage : public mergeImage {
  public:

    /**
     * Constructor
     */
    mergeHSIToImage(void);

    /**
     * return the name of this type
     */
    virtual const std::string& name() const;

    /**
     * returns a pointer to a clone of the functor.
     */
    virtual mergeHSIToImage* clone() const;

    /**
     * returns a pointer to a new instance of the functor.
     */
    virtual mergeHSIToImage* newInstance() const;

    /**
     * merge hue channel H, saturation S and intensity
     * channel I to an image
     * @param H the hue channel
     * @param S the saturation channel
     * @param I the intensity channel
     * @param img the image to be splitted
     */
    virtual bool apply(const matrix<float>& H,
                       const matrix<float>& S,
                       const matrix<float>& I,
                       image& img) const;


    /**
     * merge hue channel H, saturation S and intensity
     * channel I to an image
     * @param H the hue channel
     * @param S the saturation channel
     * @param I the intensity channel
     * @param img the image to be splitted
     */
    virtual bool apply(const matrix<ubyte>& H,
                       const matrix<ubyte>& S,
                       const matrix<ubyte>& I,
                       image& img) const;

    /**
     * merge the hue value H, saturation S and intensity value I
     * to a pixel
     * @param H the hue value
     * @param S the saturation value
     * @param I the intensity value
     * @param pixel the merged pixel
     */
    virtual bool apply(const float& H,
           const float& S,
           const float& I,
           rgbaPixel& pixel) const;

    /**
     * merge the hue value H, saturation S and intensity value I
     * to a pixel
     * @param H the hue value
     * @param S the saturation value
     * @param I the intensity value
     * @param pixel the merged pixel
     */
    virtual bool apply(const ubyte& H,
           const ubyte& S,
           const ubyte& I,
           rgbaPixel& pixel) const;

  private:
    /**
     * Some constants required to access the LUT
     */
    enum {
      Reds   = 360,  // at least 120 degrees
      Greens = 2*Reds,
      Blues  = 3*Reds,
      Sats   = 384,  // at least 256
      SatsMax = Sats-1
    };

    /**
     * matrix for HSI->RGB-conversion
     */
    static const matrix<ubyte>* DeHSI_;

    /**
     * Fix the representation in case RGB are not in a valid range.
     *
     * This method expects:
     * @param R red greater 0
     * @param G green greater 0
     * @param B blue greater 0
     *
     * The values R,G,B will be left unmodified if they are in a correct
     * range.
     */
    inline void fix(float& R,float& G,float& B) const;


  };

}

#endif