//===========================================================================
/// RGB2LAB
//===========================================================================
void SLIC::RGB2LAB(const int& sR, const int& sG, const int& sB, double& lval, double& aval, double& bval)
{
//------------------------
// sRGB to XYZ conversion
//------------------------
double X, Y, Z;
RGB2XYZ(sR, sG, sB, X, Y, Z);
//------------------------
// XYZ to LAB conversion
//------------------------
double epsilon = 0.008856; //actual CIE standard
double kappa = 903.3; //actual CIE standard
double Xr = 0.950456; //reference white
double Yr = 1.0; //reference white
double Zr = 1.088754; //reference white
double xr = X/Xr;
double yr = Y/Yr;
double zr = Z/Zr;
double fx, fy, fz;
if(xr > epsilon) fx = pow(xr, 1.0/3.0);
else fx = (kappa*xr + 16.0)/116.0;
if(yr > epsilon) fy = pow(yr, 1.0/3.0);
else fy = (kappa*yr + 16.0)/116.0;
if(zr > epsilon) fz = pow(zr, 1.0/3.0);
else fz = (kappa*zr + 16.0)/116.0;
lval = 116.0*fy-16.0;
aval = 500.0*(fx-fy);
bval = 200.0*(fy-fz);
}
void RGB2Lab3ub( unsigned char R, unsigned char G, unsigned char B, unsigned char& L, unsigned char& a, unsigned char& b )
{
float x, y, z;
float lt, at, bt;
RGB2XYZ(R, G, B, x, y, z);
XYZ2Lab(x, y, z, lt, at, bt);
L = lt;
a = at + 128;
b = bt + 128;
}
void RGB2LUVf(int R, int G, int B, float& L, float& U, float& V, bool scaled)
{
float X, Y, Z;
RGB2XYZ(R, G, B, X, Y, Z);
if (Y > 0.008856)
L = 116.0f * pow(Y, 1.0f / 3.0f) - 16.0;
else
L = 903.3f * Y;
double sum = X + 15 * Y + 3 * Z;
if(sum != 0) U = 4 * X / sum, V = 9 * Y / sum;
else U = 4.0, V = 9.0 / 15.0;
U = 13 * L * (U - 0.19784977571475);
V = 13 * L * (V - 0.46834507665248);
}
CImage *CImageRGBtoXYZ(CImage *cimg)
{
CImage *ncimg=NULL;
int p,n,i;
ncimg = CreateCImage(cimg->C[0]->ncols,cimg->C[0]->nrows);
n = ncimg->C[0]->ncols*ncimg->C[0]->nrows;
for (p=0; p < n; p++){
i = triplet(cimg->C[0]->val[p],cimg->C[1]->val[p],cimg->C[2]->val[p]);
i = RGB2XYZ(i);
ncimg->C[0]->val[p]=t0(i);
ncimg->C[1]->val[p]=t1(i);
ncimg->C[2]->val[p]=t2(i);
}
return(ncimg);
}
void RGB2Lab3f(int R, int G, int B, float& L, float& a, float& b)
{
float x, y, z;
RGB2XYZ(R, G, B, x, y, z);
XYZ2Lab(x, y, z, L, a, b);
}
LchColor RGB2Lch(const Color& rgb)
{
XYZColor xyz = RGB2XYZ(rgb);
LabColor lab = XYZ2Lab(xyz);
return Lab2Lch(lab);
}
