visibility_pyramid.cc

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// Copyright (c) 2018, ETH Zurich and UNC Chapel Hill.
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
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//     * Redistributions in binary form must reproduce the above copyright
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//     * Neither the name of ETH Zurich and UNC Chapel Hill nor the names of
//       its contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)
 
#include "base/visibility_pyramid.h"
#include "util/logging.h"
#include "util/math.h"
 
namespace colmap {
 
VisibilityPyramid::VisibilityPyramid() : VisibilityPyramid(0, 0, 0) {}
 
VisibilityPyramid::VisibilityPyramid(const size_t num_levels,
                                     const size_t width, const size_t height)
    : width_(width), height_(height), score_(0), max_score_(0) {
  pyramid_.resize(num_levels);
  for (size_t level = 0; level < num_levels; ++level) {
    const size_t level_plus_one = level + 1;
    const int dim = 1 << level_plus_one;
    pyramid_[level].setZero(dim, dim);
    max_score_ += dim * dim * dim * dim;
  }
}
 
void VisibilityPyramid::SetPoint(const double x, const double y) {
  CHECK_GT(pyramid_.size(), 0);
 
  size_t cx = 0;
  size_t cy = 0;
  CellForPoint(x, y, &cx, &cy);
 
  for (int i = static_cast<int>(pyramid_.size() - 1); i >= 0; --i) {
    auto& level = pyramid_[i];
 
    level(cy, cx) += 1;
    if (level(cy, cx) == 1) {
      score_ += level.size();
    }
 
    cx = cx >> 1;
    cy = cy >> 1;
  }
 
  CHECK_LE(score_, max_score_);
}
 
void VisibilityPyramid::ResetPoint(const double x, const double y) {
  CHECK_GT(pyramid_.size(), 0);
 
  size_t cx = 0;
  size_t cy = 0;
  CellForPoint(x, y, &cx, &cy);
 
  for (int i = static_cast<int>(pyramid_.size() - 1); i >= 0; --i) {
    auto& level = pyramid_[i];
 
    level(cy, cx) -= 1;
    if (level(cy, cx) == 0) {
      score_ -= level.size();
    }
 
    cx = cx >> 1;
    cy = cy >> 1;
  }
 
  CHECK_LE(score_, max_score_);
}
 
void VisibilityPyramid::CellForPoint(const double x, const double y, size_t* cx,
                                     size_t* cy) const {
  CHECK_GT(width_, 0);
  CHECK_GT(height_, 0);
  const int max_dim = 1 << pyramid_.size();
  *cx = Clip<size_t>(static_cast<size_t>(max_dim * x / width_), 0,
                     static_cast<size_t>(max_dim - 1));
  *cy = Clip<size_t>(static_cast<size_t>(max_dim * y / height_), 0,
                     static_cast<size_t>(max_dim - 1));
}
 
}  // namespace colmap