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/*
*
* Copyright (C) 2005-2024, Pascal Getreuer, 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"
#include "dcmtk/ofstd/ofstdinc.h" /* for STD_NAMESPACE */
#include "dcmtk/ofstd/ofcast.h"
// workaround for SunPro not defining these C functions in the global namespace
#ifdef __sun
using STD_NAMESPACE pow;
#endif
// 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, L, a, 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 = OFstatic_cast(double, (0.4123955889674142161 * R + 0.3575834307637148171 * G + 0.1804926473817015735 * B));
Y = OFstatic_cast(double, (0.2125862307855955516 * R + 0.7151703037034108499 * G + 0.07220049864333622685 * B));
Z = OFstatic_cast(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 = OFstatic_cast(double, (3.2406 * X - 1.5372 * Y - 0.4986 * Z));
G1 = OFstatic_cast(double, (-0.9689 * X + 1.8758 * Y + 0.0415 * Z));
B1 = OFstatic_cast(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);
}
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