nnls3()

void fl::colorimetric_response::nnls3 ( const float M[3][3], const float b[3], float t_out[3], float * residual_out )

inline

Definition at line 242 of file colorimetric_response.h.

                                                                    {
    float t[3] = {0.0f, 0.0f, 0.0f};
    constexpr float kStep = 0.01f;
    constexpr int kIters = 500;
    for (int it = 0; it < kIters; ++it) {
        float r[3];
        r[0] = M[0][0]*t[0] + M[0][1]*t[1] + M[0][2]*t[2] - b[0];
        r[1] = M[1][0]*t[0] + M[1][1]*t[1] + M[1][2]*t[2] - b[1];
        r[2] = M[2][0]*t[0] + M[2][1]*t[1] + M[2][2]*t[2] - b[2];
        // grad = Mᵀ · r
        float g[3];
        g[0] = M[0][0]*r[0] + M[1][0]*r[1] + M[2][0]*r[2];
        g[1] = M[0][1]*r[0] + M[1][1]*r[1] + M[2][1]*r[2];
        g[2] = M[0][2]*r[0] + M[1][2]*r[1] + M[2][2]*r[2];
        for (int j = 0; j < 3; ++j) {
            float v = t[j] - kStep * g[j];
            t[j] = v > 0.0f ? v : 0.0f;
        }
    }
    if (residual_out != nullptr) {
        float r[3];
        r[0] = M[0][0]*t[0] + M[0][1]*t[1] + M[0][2]*t[2] - b[0];
        r[1] = M[1][0]*t[0] + M[1][1]*t[1] + M[1][2]*t[2] - b[1];
        r[2] = M[2][0]*t[0] + M[2][1]*t[1] + M[2][2]*t[2] - b[2];
        *residual_out = fl::sqrt(r[0]*r[0] + r[1]*r[1] + r[2]*r[2]);
    }
    t_out[0] = t[0]; t_out[1] = t[1]; t_out[2] = t[2];
}

References fl::FL_NO_EXCEPT, fl::g, fl::sqrt(), and fl::t.

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