// Approximate a blackbody illuminant based on CHAD information
static
cmsFloat64Number CHAD2Temp(const cmsMAT3* Chad)
{
// Convert D50 across inverse CHAD to get the absolute white point
cmsVEC3 d, s;
cmsCIEXYZ Dest;
cmsCIExyY DestChromaticity;
cmsFloat64Number TempK;
cmsMAT3 m1, m2;
m1 = *Chad;
if (!_cmsMAT3inverse(&m1, &m2)) return FALSE;
s.n[VX] = cmsD50_XYZ() -> X;
s.n[VY] = cmsD50_XYZ() -> Y;
s.n[VZ] = cmsD50_XYZ() -> Z;
_cmsMAT3eval(&d, &m2, &s);
Dest.X = d.n[VX];
Dest.Y = d.n[VY];
Dest.Z = d.n[VZ];
cmsXYZ2xyY(&DestChromaticity, &Dest);
if (!cmsTempFromWhitePoint(&TempK, &DestChromaticity))
return -1.0;
return TempK;
}
// Solve a system in the form Ax = b
cmsBool CMSEXPORT _cmsMAT3solve(cmsVEC3* x, cmsMAT3* a, cmsVEC3* b)
{
cmsMAT3 m, a_1;
memmove(&m, a, sizeof(cmsMAT3));
if (!_cmsMAT3inverse(&m, &a_1)) return FALSE; // Singular matrix
_cmsMAT3eval(x, &a_1, b);
return TRUE;
}
static
cmsBool ComputeChromaticAdaptation(cmsMAT3* Conversion,
const cmsCIEXYZ* SourceWhitePoint,
const cmsCIEXYZ* DestWhitePoint,
const cmsMAT3* Chad)
{
cmsMAT3 Chad_Inv;
cmsVEC3 ConeSourceXYZ, ConeSourceRGB;
cmsVEC3 ConeDestXYZ, ConeDestRGB;
cmsMAT3 Cone, Tmp;
Tmp = *Chad;
if (!_cmsMAT3inverse(&Tmp, &Chad_Inv)) return FALSE;
_cmsVEC3init(&ConeSourceXYZ, SourceWhitePoint -> X,
SourceWhitePoint -> Y,
SourceWhitePoint -> Z);
_cmsVEC3init(&ConeDestXYZ, DestWhitePoint -> X,
DestWhitePoint -> Y,
DestWhitePoint -> Z);
_cmsMAT3eval(&ConeSourceRGB, Chad, &ConeSourceXYZ);
_cmsMAT3eval(&ConeDestRGB, Chad, &ConeDestXYZ);
// Build matrix
_cmsVEC3init(&Cone.v[0], ConeDestRGB.n[0]/ConeSourceRGB.n[0], 0.0, 0.0);
_cmsVEC3init(&Cone.v[1], 0.0, ConeDestRGB.n[1]/ConeSourceRGB.n[1], 0.0);
_cmsVEC3init(&Cone.v[2], 0.0, 0.0, ConeDestRGB.n[2]/ConeSourceRGB.n[2]);
// Normalize
_cmsMAT3per(&Tmp, &Cone, Chad);
_cmsMAT3per(Conversion, &Chad_Inv, &Tmp);
return TRUE;
}
// Build a White point, primary chromas transfer matrix from RGB to CIE XYZ
// This is just an approximation, I am not handling all the non-linear
// aspects of the RGB to XYZ process, and assumming that the gamma correction
// has transitive property in the transformation chain.
//
// the alghoritm:
//
// - First I build the absolute conversion matrix using
// primaries in XYZ. This matrix is next inverted
// - Then I eval the source white point across this matrix
// obtaining the coeficients of the transformation
// - Then, I apply these coeficients to the original matrix
//
cmsBool _cmsBuildRGB2XYZtransferMatrix(cmsMAT3* r, const cmsCIExyY* WhitePt, const cmsCIExyYTRIPLE* Primrs)
{
cmsVEC3 WhitePoint, Coef;
cmsMAT3 Result, Primaries;
cmsFloat64Number xn, yn;
cmsFloat64Number xr, yr;
cmsFloat64Number xg, yg;
cmsFloat64Number xb, yb;
xn = WhitePt -> x;
yn = WhitePt -> y;
xr = Primrs -> Red.x;
yr = Primrs -> Red.y;
xg = Primrs -> Green.x;
yg = Primrs -> Green.y;
xb = Primrs -> Blue.x;
yb = Primrs -> Blue.y;
// Build Primaries matrix
_cmsVEC3init(&Primaries.v[0], xr, xg, xb);
_cmsVEC3init(&Primaries.v[1], yr, yg, yb);
_cmsVEC3init(&Primaries.v[2], (1-xr-yr), (1-xg-yg), (1-xb-yb));
// Result = Primaries ^ (-1) inverse matrix
if (!_cmsMAT3inverse(&Primaries, &Result))
return FALSE;
_cmsVEC3init(&WhitePoint, xn/yn, 1.0, (1.0-xn-yn)/yn);
// Across inverse primaries ...
_cmsMAT3eval(&Coef, &Result, &WhitePoint);
// Give us the Coefs, then I build transformation matrix
_cmsVEC3init(&r -> v[0], Coef.n[VX]*xr, Coef.n[VY]*xg, Coef.n[VZ]*xb);
_cmsVEC3init(&r -> v[1], Coef.n[VX]*yr, Coef.n[VY]*yg, Coef.n[VZ]*yb);
_cmsVEC3init(&r -> v[2], Coef.n[VX]*(1.0-xr-yr), Coef.n[VY]*(1.0-xg-yg), Coef.n[VZ]*(1.0-xb-yb));
return _cmsAdaptMatrixToD50(r, WhitePt);
}
// Adapts a color to a given illuminant. Original color is expected to have
// a SourceWhitePt white point.
cmsBool CMSEXPORT cmsAdaptToIlluminant(cmsCIEXYZ* Result,
const cmsCIEXYZ* SourceWhitePt,
const cmsCIEXYZ* Illuminant,
const cmsCIEXYZ* Value)
{
cmsMAT3 Bradford;
cmsVEC3 In, Out;
_cmsAssert(Result != NULL);
_cmsAssert(SourceWhitePt != NULL);
_cmsAssert(Illuminant != NULL);
_cmsAssert(Value != NULL);
if (!_cmsAdaptationMatrix(&Bradford, NULL, SourceWhitePt, Illuminant)) return FALSE;
_cmsVEC3init(&In, Value -> X, Value -> Y, Value -> Z);
_cmsMAT3eval(&Out, &Bradford, &In);
Result -> X = Out.n[0];
Result -> Y = Out.n[1];
Result -> Z = Out.n[2];
return TRUE;
}
