vpColorHistogram.cpp

/*
 * ViSP, open source Visual Servoing Platform software.
 * Copyright (C) 2005 - 2025 by Inria. All rights reserved.
 *
 * This software is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * See the file LICENSE.txt at the root directory of this source
 * distribution for additional information about the GNU GPL.
 *
 * For using ViSP with software that can not be combined with the GNU
 * GPL, please contact Inria about acquiring a ViSP Professional
 * Edition License.
 *
 * See https://visp.inria.fr for more information.
 *
 * This software was developed at:
 * Inria Rennes - Bretagne Atlantique
 * Campus Universitaire de Beaulieu
 * 35042 Rennes Cedex
 * France
 *
 * If you have questions regarding the use of this file, please contact
 * Inria at visp@inria.fr
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
 
#include <visp3/rbt/vpColorHistogram.h>
 
#include <visp3/core/vpImage.h>
#include <visp3/core/vpRect.h>
 
BEGIN_VISP_NAMESPACE
 
void vpColorHistogram::Builder::build(vpColorHistogram &histogram)
{
  if (histogram.getBinNumber() != m_N) {
    throw vpException(vpException::dimensionError, "Different number of bins between builder and histogram when building histogram");
  }
  unsigned int count = 0;
  for (unsigned int i = 0; i < m_counts.size(); ++i) {
    count += m_counts[i];
  }
  const float countFloat = static_cast<float>(count);
  for (unsigned int i = 0; i < m_counts.size(); ++i) {
    histogram.m_probas[i] = static_cast<float>(m_counts[i]) / countFloat;
  }
  histogram.m_numPixels = count;
}
 
vpColorHistogram::vpColorHistogram() : m_N(0), m_binSize(0), m_numPixels(0)
{ }
 
vpColorHistogram::vpColorHistogram(unsigned int N)
{
  setBinNumber(N);
}
 
void vpColorHistogram::setBinNumber(unsigned int N)
{
  if (N != 1 && N != 2 && N != 4 && N != 8 && N != 16 && N != 32 && N != 64 && N != 128) {
    throw vpException(vpException::badValue, "The number of bins per component should be a power of 2 (below or equal to 128)");
  }
  m_N = N;
  m_binSize = 256 / m_N;
  m_numPixels = 0;
  m_probas = std::vector<float>(N * N * N, 0.f);
}
 
void vpColorHistogram::build(const vpImage<vpRGBa> &image, const vpImage<bool> &mask)
{
  std::vector<unsigned int> histo(m_N * m_N * m_N, 0);
  m_probas.resize(m_N * m_N * m_N);
  unsigned int pixels = 0;
  for (unsigned int i = 0; i < image.getSize(); ++i) {
    if (mask.bitmap[i]) {
      unsigned int index = colorToIndex(image.bitmap[i]);
      ++histo[index];
      ++pixels;
    }
  }
  m_numPixels = pixels;
  for (unsigned int i = 0; i < histo.size(); ++i) {
    m_probas[i] = static_cast<float>(histo[i]) / pixels;
  }
}
 
void vpColorHistogram::build(const std::vector<unsigned int> &counts)
{
  if (m_probas.size() != counts.size()) {
    throw vpException(vpException::dimensionError, "Number of bins are not the same");
  }
  m_probas.resize(m_N * m_N * m_N);
  m_numPixels = 0;
  for (unsigned int count : counts) {
    m_numPixels += count;
  }
  for (unsigned int i = 0; i < m_probas.size(); ++i) {
    m_probas[i] = static_cast<float>(counts[i]) / m_numPixels;
  }
}
 
void vpColorHistogram::merge(const vpColorHistogram &other, float alpha)
{
  if (other.m_N != m_N) {
    throw vpException(vpException::badValue, "Histograms should have same dimensions");
  }
  if (m_numPixels == 0) {
    m_probas = other.m_probas;
    m_numPixels = other.m_numPixels;
  }
  else {
    float malpha = 1.f - alpha;
 
    for (unsigned int i = 0; i < m_probas.size(); ++i) {
      m_probas[i] = malpha * m_probas[i] + alpha * other.m_probas[i];
    }
  }
}
 
void vpColorHistogram::computeProbas(const vpImage<vpRGBa> &image, vpImage<float> &proba) const
{
  proba.resize(image.getHeight(), image.getWidth());
#ifdef VISP_HAVE_OPENMP
#pragma omp parallel for
#endif
  for (int i = 0; i < static_cast<int>(image.getSize()); ++i) {
    proba.bitmap[i] = m_probas[colorToIndex(image.bitmap[i])];
  }
}
 
void vpColorHistogram::computeProbas(const vpImage<vpRGBa> &image, vpImage<float> &proba, const vpRect &bb) const
{
  proba.resize(image.getHeight(), image.getWidth(), 0.f);
  const int h = static_cast<int>(image.getHeight()), w = static_cast<int>(image.getWidth());
  const int top = static_cast<int>(bb.getTop());
  const int left = static_cast<int>(bb.getLeft());
  const int bottom = std::min(h- 1, static_cast<int>(bb.getBottom()));
  const int right = std::min(w - 1, static_cast<int>(bb.getRight()));
#ifdef VISP_HAVE_OPENMP
#pragma omp parallel for
#endif
  for (int i = top; i <= bottom; ++i) {
    const vpRGBa *colorRow = image[i];
    float *probaRow = proba[i];
    for (int j = left; j <= right; ++j) {
      probaRow[j] = m_probas[colorToIndex(colorRow[j])];
    }
  }
}
 
double vpColorHistogram::kl(const vpColorHistogram &other) const
{
  if (other.m_N != m_N) {
    throw vpException(vpException::badValue, "Histograms should have same dimensions");
  }
  double divergence = 0.0;
  for (unsigned int i = 0; i < m_probas.size(); ++i) {
    if (other.m_probas[i] > 0.0 && m_probas[i] > 0.0) {
      divergence += m_probas[i] * log(m_probas[i] / other.m_probas[i]);
    }
  }
  return divergence;
}
 
double vpColorHistogram::jsd(const vpColorHistogram &other) const
{
  vpColorHistogram mixture(m_N);
 
  for (unsigned int i = 0; i < m_probas.size(); ++i) {
    mixture.m_probas[i] = m_probas[i] * 0.5f + other.m_probas[i] * 0.5f;
  }
  // JSD = 0.5KL(P || M) + 0.5(Q||M) where M is the average mixture distrib of P and Q
  return (kl(mixture) + other.kl(mixture)) / 2.0;
}
 
double vpColorHistogram::hellinger(const vpColorHistogram &other) const
{
  double bcoeff = 0.0;
 
  for (unsigned int i = 0; i < m_probas.size(); ++i) {
    bcoeff += sqrt(m_probas[i] * other.m_probas[i]);
  }
 
  return sqrt(1.0 - bcoeff);
}
 
void vpColorHistogram::computeSplitHistograms(const vpImage<vpRGBa> &image, const vpImage<bool> &mask, vpColorHistogram &insideMask, vpColorHistogram &outsideMask)
{
  if (insideMask.m_N != outsideMask.m_N) {
    throw vpException(vpException::badValue, "Histograms should have same number of bins");
  }
 
  unsigned int bins = static_cast<unsigned int>(insideMask.m_probas.size());
 
  std::vector<unsigned int> countsIn(bins, 0), countsOut(bins, 0);
 
//#pragma omp parallel
  {
    std::vector<unsigned int>localCountsIn(bins, 0), localCountsOut(bins, 0);
//#pragma omp for schedule(static, 1024)
    for (unsigned int i = 0; i < image.getSize(); ++i) {
      unsigned int index = insideMask.colorToIndex(image.bitmap[i]);
      localCountsIn[index] += (mask.bitmap[i] > 0);
      localCountsOut[index] += (mask.bitmap[i] == 0);
    }
//#pragma omp critical
    {
      for (unsigned int i = 0; i < bins; ++i) {
        countsIn[i] += localCountsIn[i];
        countsOut[i] += localCountsOut[i];
      }
    }
  }
  insideMask.build(countsIn);
  outsideMask.build(countsOut);
}
 
void vpColorHistogram::computeSplitHistograms(const vpImage<vpRGBa> &image, const vpImage<bool> &mask, const vpRect &bbInside, vpColorHistogram &insideMask, vpColorHistogram &outsideMask)
{
  if (insideMask.m_N != outsideMask.m_N) {
    throw vpException(vpException::badValue, "Histograms should have same number of bins");
  }
 
  const unsigned int bins = static_cast<unsigned int>(insideMask.m_probas.size());
 
  std::vector<unsigned int> countsIn(bins, 0), countsOut(bins, 0);
 
  const int beforeBBStart = static_cast<int>(bbInside.getTop()) * image.getWidth() + static_cast<int>(bbInside.getLeft());
  const int afterBBEnd = static_cast<int>(bbInside.getBottom()) * image.getWidth() + static_cast<int>(bbInside.getRight());
#ifdef VISP_HAVE_OPENMP
#pragma omp parallel
#endif
  {
    std::vector<unsigned int>localCountsIn(bins, 0), localCountsOut(bins, 0);
#ifdef VISP_HAVE_OPENMP
#pragma omp for
#endif
    for (int i = 0; i < beforeBBStart; ++i) {
      const unsigned int index = insideMask.colorToIndex(image.bitmap[i]);
      ++localCountsOut[index];
    }
#ifdef VISP_HAVE_OPENMP
#pragma omp for
#endif
    for (int i = afterBBEnd; i < static_cast<int>(image.getSize()); ++i) {
      const unsigned int index = insideMask.colorToIndex(image.bitmap[i]);
      ++localCountsOut[index];
    }
 
#ifdef VISP_HAVE_OPENMP
#pragma omp for
#endif
    for (int i = static_cast<int>(bbInside.getTop()); i < static_cast<int>(round(bbInside.getBottom())); ++i) {
      for (int j = static_cast<int>(bbInside.getLeft()); j < static_cast<int>(round(bbInside.getRight())); ++j) {
        const unsigned int bitmapIndex = i * image.getWidth() + j;
        const unsigned int index = insideMask.colorToIndex(image.bitmap[bitmapIndex]);
        const bool pixelInMask = mask.bitmap[bitmapIndex] > 0;
        localCountsIn[index] += static_cast<unsigned int>(pixelInMask);
        localCountsOut[index] += static_cast<unsigned int>(!pixelInMask);
      }
    }
#ifdef VISP_HAVE_OPENMP
#pragma omp critical
#endif
    {
      for (unsigned int i = 0; i < bins; ++i) {
        countsIn[i] += localCountsIn[i];
        countsOut[i] += localCountsOut[i];
      }
    }
  }
  insideMask.build(countsIn);
  outsideMask.build(countsOut);
}
 
END_VISP_NAMESPACE