// Allocate conversion state structures and make look_up tables for
// the Yr,Yb,Yg <=> r,g,b conversions.
public static int TIFFCIELabToRGBInit(TIFFCIELabToRGB cielab, TIFFDisplay display, double[] refWhite)
{
cielab.range = TIFFCIELabToRGB.CIELABTORGB_TABLE_RANGE;
cielab.display.CopyTo(display);
cielab.rstep = (cielab.display.d_YCR - cielab.display.d_Y0R) / cielab.range;
cielab.gstep = (cielab.display.d_YCG - cielab.display.d_Y0G) / cielab.range;
cielab.bstep = (cielab.display.d_YCB - cielab.display.d_Y0B) / cielab.range;
double gammaR = 1.0 / cielab.display.d_gammaR;
double gammaG = 1.0 / cielab.display.d_gammaG;
double gammaB = 1.0 / cielab.display.d_gammaB;
for (int i = 0; i <= cielab.range; i++)
{
double v = (double)i / cielab.range;
cielab.Yr2r[i] = cielab.display.d_Vrwr * ((float)Math.Pow(v, gammaR));
cielab.Yg2g[i] = cielab.display.d_Vrwg * ((float)Math.Pow(v, gammaG));
cielab.Yb2b[i] = cielab.display.d_Vrwb * ((float)Math.Pow(v, gammaB));
}
// Init reference white point
cielab.X0 = (float)refWhite[0];
cielab.Y0 = (float)refWhite[1];
cielab.Z0 = (float)refWhite[2];
return(0);
}
// Allocate conversion state structures and make look_up tables for
// the Yr,Yb,Yg <=> r,g,b conversions.
public static int TIFFCIELabToRGBInit(TIFFCIELabToRGB cielab, TIFFDisplay display, double[] refWhite)
{
cielab.range=TIFFCIELabToRGB.CIELABTORGB_TABLE_RANGE;
cielab.display.CopyTo(display);
cielab.rstep=(cielab.display.d_YCR-cielab.display.d_Y0R)/cielab.range;
cielab.gstep=(cielab.display.d_YCG-cielab.display.d_Y0G)/cielab.range;
cielab.bstep=(cielab.display.d_YCB-cielab.display.d_Y0B)/cielab.range;
double gammaR=1.0/cielab.display.d_gammaR;
double gammaG=1.0/cielab.display.d_gammaG;
double gammaB=1.0/cielab.display.d_gammaB;
for(int i=0; i<=cielab.range; i++)
{
double v=(double)i/cielab.range;
cielab.Yr2r[i]=cielab.display.d_Vrwr*((float)Math.Pow(v, gammaR));
cielab.Yg2g[i]=cielab.display.d_Vrwg*((float)Math.Pow(v, gammaG));
cielab.Yb2b[i]=cielab.display.d_Vrwb*((float)Math.Pow(v, gammaB));
}
// Init reference white point
cielab.X0=(float)refWhite[0];
cielab.Y0=(float)refWhite[1];
cielab.Z0=(float)refWhite[2];
return 0;
}
// Convert color value from the XYZ space to RGB.
public static void TIFFXYZToRGB(TIFFCIELabToRGB cielab, float X, float Y, float Z, out uint r, out uint g, out uint b)
{
int i;
float Yr, Yg, Yb;
float[,] matrix = cielab.display.d_mat;
// Multiply through the matrix to get luminosity values.
Yr = matrix[0, 0] * X + matrix[0, 1] * Y + matrix[0, 2] * Z;
Yg = matrix[1, 0] * X + matrix[1, 1] * Y + matrix[1, 2] * Z;
Yb = matrix[2, 0] * X + matrix[2, 1] * Y + matrix[2, 2] * Z;
// Clip input
Yr = Math.Max(Yr, cielab.display.d_Y0R);
Yg = Math.Max(Yg, cielab.display.d_Y0G);
Yb = Math.Max(Yb, cielab.display.d_Y0B);
// Avoid overflow in case of wrong input values
Yr = Math.Min(Yr, cielab.display.d_YCR);
Yg = Math.Min(Yg, cielab.display.d_YCG);
Yb = Math.Min(Yb, cielab.display.d_YCB);
// Turn luminosity to colour value.
i = (int)((Yr - cielab.display.d_Y0R) / cielab.rstep);
i = Math.Min(cielab.range, i);
r = (uint)Math.Round(cielab.Yr2r[i], MidpointRounding.AwayFromZero);
i = (int)((Yg - cielab.display.d_Y0G) / cielab.gstep);
i = Math.Min(cielab.range, i);
g = (uint)Math.Round(cielab.Yg2g[i], MidpointRounding.AwayFromZero);
i = (int)((Yb - cielab.display.d_Y0B) / cielab.bstep);
i = Math.Min(cielab.range, i);
b = (uint)Math.Round(cielab.Yb2b[i], MidpointRounding.AwayFromZero);
// Clip output.
r = Math.Min(r, cielab.display.d_Vrwr);
g = Math.Min(g, cielab.display.d_Vrwg);
b = Math.Min(b, cielab.display.d_Vrwb);
}
// Convert color value from the CIE L*a*b* 1976 space to CIE XYZ.
public static void TIFFCIELabToXYZ(TIFFCIELabToRGB cielab, uint l, int a, int b, out float X, out float Y, out float Z)
{
float L = (float)l * 100.0F / 255.0F;
float cby, tmp;
if (L < 8.856F)
{
Y = (L * cielab.Y0) / 903.292F;
cby = 7.787F * (Y / cielab.Y0) + 16.0F / 116.0F;
}
else
{
cby = (L + 16.0F) / 116.0F;
Y = cielab.Y0 * cby * cby * cby;
}
tmp = (float)a / 500.0F + cby;
if (tmp < 0.2069F)
{
X = cielab.X0 * (tmp - 0.13793F) / 7.787F;
}
else
{
X = cielab.X0 * tmp * tmp * tmp;
}
tmp = cby - (float)b / 200.0F;
if (tmp < 0.2069F)
{
Z = cielab.Z0 * (tmp - 0.13793F) / 7.787F;
}
else
{
Z = cielab.Z0 * tmp * tmp * tmp;
}
}
// Convert color value from the CIE L*a*b* 1976 space to CIE XYZ.
public static void TIFFCIELabToXYZ(TIFFCIELabToRGB cielab, uint l, int a, int b, out float X, out float Y, out float Z)
{
float L=(float)l*100.0F/255.0F;
float cby, tmp;
if(L<8.856F)
{
Y=(L*cielab.Y0)/903.292F;
cby=7.787F*(Y/cielab.Y0)+16.0F/116.0F;
}
else
{
cby=(L+16.0F)/116.0F;
Y=cielab.Y0*cby*cby*cby;
}
tmp=(float)a/500.0F+cby;
if(tmp<0.2069F) X=cielab.X0*(tmp-0.13793F)/7.787F;
else X=cielab.X0*tmp*tmp*tmp;
tmp=cby-(float)b/200.0F;
if(tmp<0.2069F) Z=cielab.Z0*(tmp-0.13793F)/7.787F;
else Z=cielab.Z0*tmp*tmp*tmp;
}
// Convert color value from the XYZ space to RGB.
public static void TIFFXYZToRGB(TIFFCIELabToRGB cielab, float X, float Y, float Z, out uint r, out uint g, out uint b)
{
int i;
float Yr, Yg, Yb;
float[,] matrix=cielab.display.d_mat;
// Multiply through the matrix to get luminosity values.
Yr=matrix[0, 0]*X+matrix[0, 1]*Y+matrix[0, 2]*Z;
Yg=matrix[1, 0]*X+matrix[1, 1]*Y+matrix[1, 2]*Z;
Yb=matrix[2, 0]*X+matrix[2, 1]*Y+matrix[2, 2]*Z;
// Clip input
Yr=Math.Max(Yr, cielab.display.d_Y0R);
Yg=Math.Max(Yg, cielab.display.d_Y0G);
Yb=Math.Max(Yb, cielab.display.d_Y0B);
// Avoid overflow in case of wrong input values
Yr=Math.Min(Yr, cielab.display.d_YCR);
Yg=Math.Min(Yg, cielab.display.d_YCG);
Yb=Math.Min(Yb, cielab.display.d_YCB);
// Turn luminosity to colour value.
i=(int)((Yr-cielab.display.d_Y0R)/cielab.rstep);
i=Math.Min(cielab.range, i);
r=(uint)Math.Round(cielab.Yr2r[i], MidpointRounding.AwayFromZero);
i=(int)((Yg-cielab.display.d_Y0G)/cielab.gstep);
i=Math.Min(cielab.range, i);
g=(uint)Math.Round(cielab.Yg2g[i], MidpointRounding.AwayFromZero);
i=(int)((Yb-cielab.display.d_Y0B)/cielab.bstep);
i=Math.Min(cielab.range, i);
b=(uint)Math.Round(cielab.Yb2b[i], MidpointRounding.AwayFromZero);
// Clip output.
r=Math.Min(r, cielab.display.d_Vrwr);
g=Math.Min(g, cielab.display.d_Vrwg);
b=Math.Min(b, cielab.display.d_Vrwb);
}
