Function solve_wx_overdrive

src/fl/gfx/rgbw_colorimetric.cpp.hpp:789–859

Boosted / overdrive solver. This remains useful as an optional visual policy, but it is deliberately distinct from wx_lp_legacy. The non-overdriven residual boundary gives the chromaticity-preserving W limit; overdrive_ratio then moves W toward 1.0 and accepts the corresponding drift toward the W diode.

// chromaticity-preserving W limit; overdrive_ratio then moves W toward 1.0 and
// accepts the corresponding drift toward the W diode.
void solve_wx_overdrive(const ProfileCache& cache, float s_r, float s_g,
                        float s_b, float overdrive_ratio,
                        float out_rgbw[4]) FL_NOEXCEPT {
    zero4(out_rgbw);

    const float value = max3f(s_r, s_g, s_b);
    if (value <= 1e-9f) {
        return;
    }

    // Boosted/overdrive is a distinct visual policy, but it still must keep
    // native single/dual topology authority. Single axes stay exact; dual
    // edges stay locked to RG/RB/GB through the measured two-emitter solve.
    if (is_native_input_gamut(*cache.profile)) {
        const int n_active = count_active_channels(s_r, s_g, s_b);
        if (n_active == 1) {
            native_single_identity(s_r, s_g, s_b, out_rgbw);
            return;
        }
        if (n_active == 2) {
            solve_native_dual_edge_fixed_topology(cache, s_r, s_g,
                                                  s_b, out_rgbw);
            return;
        }
    }

    // Solve the full-chroma endpoint first and scale value later. This keeps
    // boosted mode from flattening fixed-hue HSV value ramps into repeated
    // saturated endpoint tuples.
    const float c_r = s_r / value;
    const float c_g = s_g / value;
    const float c_b = s_b / value;

    float X_t[3];
    source_rgb_to_XYZ(cache, c_r, c_g, c_b, X_t);

    float xy_t[2];
    project_to_hull(cache, X_t, xy_t);

    float a[3];
    matvec3(cache.P_RGB_inv, X_t, a);
    const float* d = cache.d_W;

    float w_strict = 1.0f;
    for (int i = 0; i < 3; ++i) {
        if (d[i] > 1e-9f && a[i] >= 0.0f) {
            const float lim = a[i] / d[i];
            if (lim < w_strict) {
                w_strict = lim;
            }
        }
    }
    w_strict = fl::clamp(w_strict, 0.0f, 1.0f);

    const float rho = fl::clamp(overdrive_ratio, 0.0f, 1.0f);
    float w = w_strict + rho * (1.0f - w_strict);
    w = fl::clamp(w, 0.0f, 1.0f);