Function build_source_matrix

src/fl/gfx/rgbw_colorimetric.h:139–164

Standard CIE primary-matrix construction (#2705). Given source primary chromaticities xy_r/g/b and a source white chromaticity xy_w, build the 3x3 matrix M such that M·[1,1,1]^T = xyY_to_XYZ(xy_w, 1.0). Columns are per-channel scaled XYZ vectors of the primaries at Y=1, with scaling chosen so the (1,1,1) input lands at source white in XYZ. This is the classic linear-sRGB -> XYZ derivation generali

// classic linear-sRGB -> XYZ derivation generalized to arbitrary primaries.
// Returns false if the primary matrix is singular (collinear chromaticities).
inline bool build_source_matrix(const float xy_r[2], const float xy_g[2],
                                const float xy_b[2], const float xy_w[2],
                                float M_out[3][3]) FL_NOEXCEPT {
    float xyz_R[3], xyz_G[3], xyz_B[3], xyz_W[3];
    xyY_to_XYZ(xy_r[0], xy_r[1], 1.0f, xyz_R);
    xyY_to_XYZ(xy_g[0], xy_g[1], 1.0f, xyz_G);
    xyY_to_XYZ(xy_b[0], xy_b[1], 1.0f, xyz_B);
    xyY_to_XYZ(xy_w[0], xy_w[1], 1.0f, xyz_W);

    float P[3][3];
    P[0][0] = xyz_R[0]; P[0][1] = xyz_G[0]; P[0][2] = xyz_B[0];
    P[1][0] = xyz_R[1]; P[1][1] = xyz_G[1]; P[1][2] = xyz_B[1];
    P[2][0] = xyz_R[2]; P[2][1] = xyz_G[2]; P[2][2] = xyz_B[2];

    float P_inv[3][3];
    if (!invert3x3(P, P_inv)) {
        return false;
    }
    float k[3];
    matvec3(P_inv, xyz_W, k);

    M_out[0][0] = k[0] * xyz_R[0]; M_out[0][1] = k[1] * xyz_G[0]; M_out[0][2] = k[2] * xyz_B[0];
    M_out[1][0] = k[0] * xyz_R[1]; M_out[1][1] = k[1] * xyz_G[1]; M_out[1][2] = k[2] * xyz_B[1];
    M_out[2][0] = k[0] * xyz_R[2]; M_out[2][1] = k[1] * xyz_G[2]; M_out[2][2] = k[2] * xyz_B[2];
    return true;
}

// Native-gamut detection (#2748). Returns true when the source primaries
// of `p` (input_xy_r/g/b) match the LED's measured primaries (xy_r/g/b)