MaxPointCount.cpp

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// kate: replace-tabs off; indent-width 4; indent-mode normal
// vim: ts=4:sw=4:noexpandtab
/*

Copyright (c) 2010--2018,
François Pomerleau and Stephane Magnenat, ASL, ETHZ, Switzerland
You can contact the authors at <f dot pomerleau at gmail dot com> and
<stephane at magnenat dot net>

All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
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      notice, this list of conditions and the following disclaimer.
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      documentation and/or other materials provided with the distribution.
    * Neither the name of the <organization> nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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*/
#include "MaxPointCount.h"
#include <random>

// MaxPointCountDataPointsFilter
// Constructor
template<typename T>
MaxPointCountDataPointsFilter<T>::MaxPointCountDataPointsFilter(const Parameters& params):
        PointMatcher<T>::DataPointsFilter("MaxPointCountDataPointsFilter",
                                                                          MaxPointCountDataPointsFilter::availableParameters(), params),
        maxCount(Parametrizable::get<size_t>("maxCount"))
{
        try
        {
                seed = this->template get<size_t>("seed");
        }
        catch (const InvalidParameter&)
        {
                seed = static_cast<size_t>(1); // rand default seed number
        }
}

// Compute
template<typename T>
typename PointMatcher<T>::DataPoints MaxPointCountDataPointsFilter<T>::filter(const DataPoints& input)
{
        DataPoints output(input);
        inPlaceFilter(output);
        return output;
}

// In-place filter
template<typename T>
void MaxPointCountDataPointsFilter<T>::inPlaceFilter(DataPoints& cloud)
{
        const size_t N{static_cast<size_t>(cloud.getNbPoints() - 1)};

        if (maxCount <= N)
        {
                std::minstd_rand randomNumberGenerator(static_cast<std::uint_fast32_t>(seed));
                std::uniform_real_distribution<float> distribution{0, 1};

                for (size_t j{0u}; j < maxCount; ++j)
                {
                        //Get a random index in [j; N]
                        const size_t index{j + static_cast<size_t>((N - j) * distribution(randomNumberGenerator))};

                        //Switch columns j and index
                        cloud.swapCols(j, index);
                }
                //Resize the cloud
                cloud.conservativeResize(maxCount);
        }
}

template struct MaxPointCountDataPointsFilter<float>;
template struct MaxPointCountDataPointsFilter<double>;