%ffp

/************* Header *************/
//Filter Identification
Category: "Hidetaka Filter"
Title: "sRGB to Lab"
Filename:"FM_sRGBtoLab.8bf"
Author: "Hidetaka Hama"
Copyright: "2001 Hidetaka Hama"


/******* Program Description *******/

ForEveryTile:
{

/* D65 White point */
double Xw65 = 0.9504;
double Yw65 = 1.0000;
double Zw65 = 1.0889;


/* D50 White point */
double Xw50 = 0.9642;
double Yw50 = 1.0000;
double Zw50 = 0.8249;

/* Pixel Value Temp */
double ri,gi,bi;
double gr,gg,gb;
double x65,y65,z65;
double x50,y50,z50;
double xx50,yy50,zz50;
double lo,ao,bo;



for (y=0; y<ymax; y++) {
for (x=0; x<xmax; x++) {

/*---------- Range Change from 255 ----------*/

    ri = src(x,y,0)/255.0;
    gi = src(x,y,1)/255.0;
    bi = src(x,y,2)/255.0;

    if (ri <= 0.03928) {
        gr = ri/12.92;
    } else {
        gr = pow((ri+0.055)/1.055,2.4);
    }

    if (gi <= 0.03928) {
        gg = gi/12.92;
    } else {
        gg = pow((gi+0.055)/1.055,2.4);
    }

    if (bi <= 0.03928) {
        gb = bi/12.92;
    } else {
        gb = pow((bi+0.055)/1.055,2.4);
    }


/*---------- sRGB(D65) to XYZ(D65) ----------*/

    x65 =  0.4124*gr + 0.3576*gg + 0.1805*gb;
    y65 =  0.2126*gr + 0.7152*gg + 0.0722*gb;
    z65 =  0.0193*gr + 0.1192*gg + 0.9505*gb;

/*---------- XYZ(D65) to XYZ(D50) ----------*/

    x50 =  1.0282015*x65 + 0.0500707*y65 - 0.0579688*z65;
    y50 =  0.0197032*x65 + 0.9871848*y65 - 0.0054285*z65;
    z50 = -0.0002329*x65 + 0.0006862*y65 + 0.7573070*z65;

/*---------- XYZ(D50) to Lab(D50) ----------*/

    if ((x50/Xw50)>0.008856) {
        xx50 = pow(x50/Xw50,1.0/3.0);
    } else {
        xx50 = 7.78*(x50/Xw50) + 16.0/116.0;
    }

    if ((y50/Yw50)>0.008856) {
        yy50 = pow(y50/Yw50,1.0/3.0);
    } else {
        yy50 = 7.78*(y50/Yw50) + 16.0/116.0;
    }

    if ((z50/Zw50)>0.008856) {
        zz50 = pow(z50/Zw50,1.0/3.0);
    } else {
        zz50 = 7.78*(z50/Zw50) + 16.0/116.0;
    }


    lo = 116.0 * yy50 - 16.0;
    ao = 500.0 * (xx50-yy50);
    bo = 200.0 * (yy50-zz50);

/*---------- Range Change to 255 ----------*/

        lo = lo * 255.0 / 100.0;
        ao = ao + 128.0;
        bo = bo + 128.0;


/*------------- Output Buffer -------------*/

    pset(x,y,0,(int)lo);
    pset(x,y,1,(int)ao);
    pset(x,y,2,(int)bo);

}
updateProgress(y,Y);
updatePreview(a);

}

return true;
}