visibility_pyramid.h

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// ----------------------------------------------------------------------------
// -                        CloudViewer: www.cloudViewer.org                  -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2024 www.cloudViewer.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#pragma once
 
#include <Eigen/Core>
#include <vector>
 
#include "util/alignment.h"
 
namespace colmap {
 
// A class that captures the distribution of points in a 2D grid.
// For example, to capture the distribution of visible 3D points in an image.
//
// The class captures the distribution of points by a score. A higher score
// corresponds to a more uniform distribution of the points in the grid.
//
// The score is computed by the number of populated cells in a multi-resolution
// pyramid. A populated cell contributes to the overall score if it is
// populated by at least one point and the contributed score is according
// to its resolution in the pyramid. A cell in a higher resolution level
// contributes a higher score to the overall score.
class VisibilityPyramid {
public:
    VisibilityPyramid();
    VisibilityPyramid(const size_t num_levels,
                      const size_t width,
                      const size_t height);
 
    void SetPoint(const double x, const double y);
    void ResetPoint(const double x, const double y);
 
    inline size_t NumLevels() const;
    inline size_t Width() const;
    inline size_t Height() const;
 
    inline size_t Score() const;
    inline size_t MaxScore() const;
 
private:
    void CellForPoint(const double x,
                      const double y,
                      size_t* cx,
                      size_t* cy) const;
 
    // Range of the input points.
    size_t width_;
    size_t height_;
 
    // The overall visibility score.
    size_t score_;
 
    // The maximum score when all cells are populated.
    size_t max_score_;
 
    // The visibilty pyramid with multiple levels.
    std::vector<Eigen::MatrixXi> pyramid_;
};
 
// Implementation
 
size_t VisibilityPyramid::NumLevels() const { return pyramid_.size(); }
 
size_t VisibilityPyramid::Width() const { return width_; }
 
size_t VisibilityPyramid::Height() const { return height_; }
 
size_t VisibilityPyramid::Score() const { return score_; }
 
size_t VisibilityPyramid::MaxScore() const { return max_score_; }
 
}  // namespace colmap