/*
 *
 *  Copyright (C) 2005-2010, Pascal Getreuer
 *  Copyright (C) 2016, Open Connections GmbH
 *  All rights reserved.  See COPYRIGHT file for details.
 *
 *  This software and supporting documentation are maintained by
 *
 *    OFFIS e.V.
 *    R&D Division Health
 *    Escherweg 2
 *    D-26121 Oldenburg, Germany
 *
 *
 *  Module:  dcmiod
 *
 *  Author:  Pascal Getreuer, Michael Onken
 *
 *  Purpose: Static helper functionality for CIE<->RGB color conversions
 *
 */
#include "dcmtk/config/osconfig.h"
#include "dcmtk/dcmiod/cielabutil.h"
#define INCLUDE_CMATH                // for pow() function
#include "dcmtk/ofstd/ofstdinc.h"

// Initialize white points of D65 light point (CIELab standard white point)
const double IODCIELabUtil::D65_WHITEPOINT_X = 0.950456;
const double IODCIELabUtil::D65_WHITEPOINT_Y = 1.0;
const double IODCIELabUtil::D65_WHITEPOINT_Z = 1.088754;


void IODCIELabUtil::dicomLab2RGB(double& R, double& G, double& B, double LDicom, double aDicom, double bDicom)
{
  double L, a, b;
  dicomlab2Lab(L, a, b, LDicom, aDicom, bDicom);
  lab2Rgb(R, G, B, L, a, b);
}


void IODCIELabUtil::rgb2DicomLab(double& LDicom, double& aDicom, double& bDicom, double R, double G, double B)
{
  double L, a, b;
  rgb2Lab(L, a, b, R, G, B);
  lab2DicomLab(LDicom, aDicom, bDicom, R, G, B);
}


void IODCIELabUtil::dicomlab2Lab(double& L, double& a, double& b, double LDicom, double aDicom, double bDicom)
{
  L = ((LDicom * 100.0) / 65535.0); // results in 0 <= L <= 100
  a = ((aDicom * 255.0) / 65535.0) - 128; // results in -128 <= a <= 127
  b = ((bDicom * 255.0) / 65535.0) - 128; // results in -128 <= b <= 127
}


void IODCIELabUtil::lab2DicomLab(double& LDicom, double& aDicom, double& bDicom, double L, double a, double b)
{
  LDicom = L * 65535.0 / 100.0; // results in 0 <= L <= 65535
  aDicom = (a + 128) * 65535.0 / 255.0; // results in 0 <= a <= 65535
  bDicom = (b + 128) * 65535.0 / 255.0; // results in 0 <= b <= 65535
}


void IODCIELabUtil::rgb2Lab(double& L, double& a, double& b, double R, double G, double B)
{
  double X, Y, Z;
  rgb2Xyz(X, Y, Z, R, G, B);
  xyz2Lab(L, a, b, X, Y, Z);
}


double IODCIELabUtil::gammaCorrection(double n)
{
  if ((n) <= 0.0031306684425005883)
  {
    return 12.92 * (n);
  }
  else
  {
    return (1.055*pow((n), 0.416666666666666667) - 0.055);
  }
}


double IODCIELabUtil::invGammaCorrection(double n)
{
  if ((n) <= 0.0404482362771076)
  {
    return ((n) / 12.92);
  }
  else
  {
    return ( pow(((n) + 0.055)/1.055, 2.4) );
  }
}


void IODCIELabUtil::rgb2Xyz(double& X, double& Y, double& Z, double R, double G, double B)
{
  R = invGammaCorrection(R);
  G = invGammaCorrection(G);
  B = invGammaCorrection(B);
  X = (double)(0.4123955889674142161*R + 0.3575834307637148171*G + 0.1804926473817015735*B);
  Y = (double)(0.2125862307855955516*R + 0.7151703037034108499*G + 0.07220049864333622685*B);
  Z = (double)(0.01929721549174694484*R + 0.1191838645808485318*G + 0.9504971251315797660*B);
}


void IODCIELabUtil::xyz2Lab(double& L, double& a, double& b, double X, double Y, double Z)
{
  X /= D65_WHITEPOINT_X;
  Y /= D65_WHITEPOINT_Y;
  Z /= D65_WHITEPOINT_Z;
  X = labf(X);
  Y = labf(Y);
  Z = labf(Z);
  L = 116*Y - 16;
  a = 500*(X - Y);
  b = 200*(Y - Z);
}


void IODCIELabUtil::lab2Rgb(double& R, double& G, double& B, double L, double a, double b)
{
  double  X, Y, Z;
  lab2Xyz(X, Y, Z, L, a, b);
  xyz2Rgb(R, G, B, X, Y, Z);
}


void IODCIELabUtil::lab2Xyz(double& X, double& Y, double& Z, double L, double a, double b)
{
  L = (L + 16)/116;
  a = L + a/500;
  b = L - b/200;
  X = D65_WHITEPOINT_X * labfInv(a);
  Y = D65_WHITEPOINT_Y * labfInv(L);
  Z = D65_WHITEPOINT_Z * labfInv(b);
}


void IODCIELabUtil::xyz2Rgb(double& R, double& G, double& B, double X, double Y, double Z)
{
  double R1, B1, G1, Min;

  R1 = (double)( 3.2406*X - 1.5372*Y - 0.4986*Z);
  G1 = (double)(-0.9689*X + 1.8758*Y + 0.0415*Z);
  B1 = (double)( 0.0557*X - 0.2040*Y + 1.0570*Z);

  Min = min3(R1, G1, B1);

  /* Force nonnegative values so that gamma correction is well-defined. */
  if(Min < 0)
  {
    R1 -= Min;
    G1 -= Min;
    B1 -= Min;
  }

  /* Transform from RGB to R'G'B' */
  R = gammaCorrection(R1);
  G = gammaCorrection(G1);
  B = gammaCorrection(B1);
}


double IODCIELabUtil::labf(double n)
{
  if (n >= 8.85645167903563082e-3)
  {
    return ( pow(n, 0.333333333333333) );
  }
  else
  {
    return ( (841.0/108.0)*(n) + (4.0/29.0) );
  }
}


double IODCIELabUtil::labfInv(double n)
{
  if ( (n) >= 0.206896551724137931 )
  {
    return (n)*(n)*(n);
  }
  else
  {
    return (108.0/841.0)*((n) - (4.0/29.0));
  }
}


double IODCIELabUtil::min2(double a, double b)
{
  if (a <= b)
    return a;
  else
    return b;
}


double IODCIELabUtil::min3(double a, double b, double c)
{
  if (a <= b)
    return min2(a,c);
  else
    return min2(b,c);
}
