Jungfraujoch/image_analysis/image_preprocessing/SaturationCeiling.cpp

// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#include "SaturationCeiling.h"

#include <algorithm>
#include <cmath>

namespace saturation_ceiling {

namespace {

int Bin(int64_t value) {
    return static_cast<int>(std::floor(std::log2(static_cast<double>(value) / FLOOR) * BINS_PER_OCTAVE));
}

int64_t LowerEdge(int bin) {
    return static_cast<int64_t>(std::ceil(FLOOR * std::exp2(static_cast<double>(bin) / BINS_PER_OCTAVE)));
}

}  // namespace

void Add(Histogram &h, int64_t value) {
    if (value < FLOOR)
        return;
    const int b = Bin(value);
    if (b < N_BINS)
        h[b]++;
}

void Add(Histogram &h, const std::vector<int32_t> &values, const std::vector<uint32_t> &mask) {
    for (size_t i = 0; i < values.size(); i++)
        if (i >= mask.size() || mask[i] == 0)
            Add(h, values[i]);
}

std::optional<int64_t> Ceiling(const Histogram &h) {
    for (int b = WINDOW; b < N_BINS; b++) {
        const uint64_t below = *std::max_element(h.begin() + b - WINDOW, h.begin() + b);
        if (h[b] >= MIN_PIXELS && static_cast<double>(h[b]) > RISE * static_cast<double>(below))
            return LowerEdge(b);
    }
    return std::nullopt;
}

}  // namespace saturation_ceiling