histogram.h

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/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi Ltd
 *
 * histogram calculation interface
 */
 
#pragma once
 
#include <limits.h>
#include <span>
#include <stdint.h>
#include <type_traits>
#include <vector>
 
#include <libcamera/base/utils.h>
 
namespace libcamera {
 
namespace ipa {
 
class Histogram
{
public:
    Histogram() { cumulative_.push_back(0); }
    Histogram(std::span<const uint32_t> data);
 
    template<typename Transform,
         std::enable_if_t<std::is_invocable_v<Transform, uint32_t>> * = nullptr>
    Histogram(std::span<const uint32_t> data, Transform transform)
    {
        cumulative_.resize(data.size() + 1);
        cumulative_[0] = 0;
        for (const auto &[i, value] : utils::enumerate(data))
            cumulative_[i + 1] = cumulative_[i] + transform(value);
    }
 
    size_t bins() const { return cumulative_.size() - 1; }
    std::span<const uint64_t> data() const { return cumulative_; }
    uint64_t total() const { return cumulative_.back(); }
    uint64_t cumulativeFrequency(double bin) const;
    double quantile(double q, uint32_t first = 0, uint32_t last = UINT_MAX) const;
    double interQuantileMean(double lowQuantile, double hiQuantile) const;
 
    uint32_t operator[](size_t bin) const
    {
        return cumulative_[bin + 1] - cumulative_[bin];
    }
 
private:
    std::vector<uint64_t> cumulative_;
};
 
} /* namespace ipa */
 
} /* namespace libcamera */