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Statistics.h
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// Copyright Contributors to the OpenVDB Project
// SPDX-License-Identifier: MPL-2.0
//
/// @file Statistics.h
///
/// @brief Functions to efficiently compute histograms, extrema
/// (min/max) and statistics (mean, variance, etc.) of grid values
#ifndef OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
#define OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
#include <openvdb/Types.h>
#include <openvdb/Exceptions.h>
#include <openvdb/math/Stats.h>
#include "ValueTransformer.h"
namespace openvdb {
OPENVDB_USE_VERSION_NAMESPACE
namespace OPENVDB_VERSION_NAME {
namespace tools {
/// @brief Iterate over a scalar grid and compute a histogram of the values
/// of the voxels that are visited, or iterate over a vector-valued grid
/// and compute a histogram of the magnitudes of the vectors.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param minVal the smallest value that can be added to the histogram
/// @param maxVal the largest value that can be added to the histogram
/// @param numBins the number of histogram bins
/// @param threaded if true, iterate over the grid in parallel
template<typename IterT>
inline math::Histogram
histogram(const IterT& iter, double minVal, double maxVal,
size_t numBins = 10, bool threaded = true);
/// @brief Iterate over a scalar grid and compute extrema (min/max) of the
/// values of the voxels that are visited, or iterate over a vector-valued grid
/// and compute extrema of the magnitudes of the vectors.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param threaded if true, iterate over the grid in parallel
template<typename IterT>
inline math::Extrema
extrema(const IterT& iter, bool threaded = true);
/// @brief Iterate over a scalar grid and compute statistics (mean, variance, etc.)
/// of the values of the voxels that are visited, or iterate over a vector-valued grid
/// and compute statistics of the magnitudes of the vectors.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param threaded if true, iterate over the grid in parallel
template<typename IterT>
inline math::Stats
statistics(const IterT& iter, bool threaded = true);
/// @brief Iterate over a grid and compute extrema (min/max) of
/// the values produced by applying the given functor at each voxel that is visited.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param op a functor of the form <tt>void op(const IterT&, math::Stats&)</tt>,
/// where @c IterT is the type of @a iter, that inserts zero or more
/// floating-point values into the provided @c math::Stats object
/// @param threaded if true, iterate over the grid in parallel
/// @note When @a threaded is true, each thread gets its own copy of the functor.
///
/// @par Example:
/// Compute statistics of just the active and positive-valued voxels of a scalar,
/// floating-point grid.
/// @code
/// struct Local {
/// static inline
/// void addIfPositive(const FloatGrid::ValueOnCIter& iter, math::Extrema& ex)
/// {
/// const float f = *iter;
/// if (f > 0.0) {
/// if (iter.isVoxelValue()) ex.add(f);
/// else ex.add(f, iter.getVoxelCount());
/// }
/// }
/// };
/// FloatGrid grid = ...;
/// math::Extrema stats =
/// tools::extrema(grid.cbeginValueOn(), Local::addIfPositive, /*threaded=*/true);
/// @endcode
template<typename IterT, typename ValueOp>
inline math::Extrema
extrema(const IterT& iter, const ValueOp& op, bool threaded);
/// @brief Iterate over a grid and compute statistics (mean, variance, etc.) of
/// the values produced by applying the given functor at each voxel that is visited.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param op a functor of the form <tt>void op(const IterT&, math::Stats&)</tt>,
/// where @c IterT is the type of @a iter, that inserts zero or more
/// floating-point values into the provided @c math::Stats object
/// @param threaded if true, iterate over the grid in parallel
/// @note When @a threaded is true, each thread gets its own copy of the functor.
///
/// @par Example:
/// Compute statistics of just the active and positive-valued voxels of a scalar,
/// floating-point grid.
/// @code
/// struct Local {
/// static inline
/// void addIfPositive(const FloatGrid::ValueOnCIter& iter, math::Stats& stats)
/// {
/// const float f = *iter;
/// if (f > 0.0) {
/// if (iter.isVoxelValue()) stats.add(f);
/// else stats.add(f, iter.getVoxelCount());
/// }
/// }
/// };
/// FloatGrid grid = ...;
/// math::Stats stats =
/// tools::statistics(grid.cbeginValueOn(), Local::addIfPositive, /*threaded=*/true);
/// @endcode
template<typename IterT, typename ValueOp>
inline math::Stats
statistics(const IterT& iter, const ValueOp& op, bool threaded);
/// @brief Iterate over a grid and compute statistics (mean, variance, etc.)
/// of the values produced by applying a given operator (see math/Operators.h)
/// at each voxel that is visited.
/// @param iter an iterator over the values of a grid or its tree
/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
/// @param op an operator object with a method of the form
/// <tt>double result(Accessor&, const Coord&)</tt>
/// @param threaded if true, iterate over the grid in parallel
/// @note World-space operators, whose @c result() methods are of the form
/// <tt>double result(const Map&, Accessor&, const Coord&)</tt>, must be wrapped
/// in a math::MapAdapter.
/// @note Vector-valued operators like math::Gradient must be wrapped in an adapter
/// such as math::OpMagnitude.
///
/// @par Example:
/// Compute statistics of the magnitude of the gradient at the active voxels of
/// a scalar, floating-point grid. (Note the use of the math::MapAdapter and
/// math::OpMagnitude adapters.)
/// @code
/// FloatGrid grid = ...;
///
/// // Assume that we know that the grid has a uniform scale map.
/// using MapType = math::UniformScaleMap;
/// // Specify a world-space gradient operator that uses first-order differencing.
/// using GradientOp = math::Gradient<MapType, math::FD_1ST>;
/// // Wrap the operator with an adapter that computes the magnitude of the gradient.
/// using MagnitudeOp = math::OpMagnitude<GradientOp, MapType>;
/// // Wrap the operator with an adapter that associates a map with it.
/// using CompoundOp = math::MapAdapter<MapType, GradientOp, double>;
///
/// if (MapType::Ptr map = grid.constTransform().constMap<MapType>()) {
/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), CompoundOp(*map));
/// }
/// @endcode
///
/// @par Example:
/// Compute statistics of the divergence at the active voxels of a vector-valued grid.
/// @code
/// Vec3SGrid grid = ...;
///
/// // Assume that we know that the grid has a uniform scale map.
/// using MapType = math::UniformScaleMap;
/// // Specify a world-space divergence operator that uses first-order differencing.
/// using DivergenceOp = math::Divergence<MapType, math::FD_1ST>;
/// // Wrap the operator with an adapter that associates a map with it.
/// using CompoundOp = math::MapAdapter<MapType, DivergenceOp, double>;
///
/// if (MapType::Ptr map = grid.constTransform().constMap<MapType>()) {
/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), CompoundOp(*map));
/// }
/// @endcode
///
/// @par Example:
/// As above, but computing the divergence in index space.
/// @code
/// Vec3SGrid grid = ...;
///
/// // Specify an index-space divergence operator that uses first-order differencing.
/// using DivergenceOp = math::ISDivergence<math::FD_1ST>;
///
/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), DivergenceOp());
/// @endcode
template<typename OperatorT, typename IterT>
inline math::Stats
opStatistics(const IterT& iter, const OperatorT& op = OperatorT(), bool threaded = true);
/// @brief Same as opStatistics except it returns a math::Extrema vs a math::Stats
template<typename OperatorT, typename IterT>
inline math::Extrema
opExtrema(const IterT& iter, const OperatorT& op = OperatorT(), bool threaded = true);
////////////////////////////////////////
/// @cond OPENVDB_DOCS_INTERNAL
namespace stats_internal {
/// @todo This traits class is needed because tree::TreeValueIteratorBase uses
/// the name ValueT for the type of the value to which the iterator points,
/// whereas node-level iterators use the name ValueType.
template<typename IterT, typename AuxT = void>
struct IterTraits {
using ValueType = typename IterT::ValueType;
};
template<typename TreeT, typename ValueIterT>
struct IterTraits<tree::TreeValueIteratorBase<TreeT, ValueIterT> > {
using ValueType = typename tree::TreeValueIteratorBase<TreeT, ValueIterT>::ValueT;
};
// Helper class to compute a scalar value from either a scalar or a vector value
// (the latter by computing the vector's magnitude)
template<typename T, bool IsVector> struct GetValImpl;
template<typename T>
struct GetValImpl<T, /*IsVector=*/false> {
static inline double get(const T& val) { return double(val); }
};
template<typename T>
struct GetValImpl<T, /*IsVector=*/true> {
static inline double get(const T& val) { return val.length(); }
};
// Helper class to compute a scalar value from a tree or node iterator
// that points to a value in either a scalar or a vector grid, and to
// add that value to a math::Stats object.
template<typename IterT, typename StatsT>
struct GetVal
{
using ValueT = typename IterTraits<IterT>::ValueType;
using ImplT = GetValImpl<ValueT, VecTraits<ValueT>::IsVec>;
inline void operator()(const IterT& iter, StatsT& stats) const {
if (iter.isVoxelValue()) stats.add(ImplT::get(*iter));
else stats.add(ImplT::get(*iter), iter.getVoxelCount());
}
};
// Helper class to accumulate scalar voxel values or vector voxel magnitudes
// into a math::Stats object
template<typename IterT, typename ValueOp, typename StatsT>
struct StatsOp
{
StatsOp(const ValueOp& op): getValue(op) {}
// Accumulate voxel and tile values into this functor's Stats object.
inline void operator()(const IterT& iter) { getValue(iter, stats); }
// Accumulate another functor's Stats object into this functor's.
inline void join(StatsOp& other) { stats.add(other.stats); }
StatsT stats;
ValueOp getValue;
};
// Helper class to accumulate scalar voxel values or vector voxel magnitudes
// into a math::Histogram object
template<typename IterT, typename ValueOp>
struct HistOp
{
HistOp(const ValueOp& op, double vmin, double vmax, size_t bins):
hist(vmin, vmax, bins), getValue(op)
{}
// Accumulate voxel and tile values into this functor's Histogram object.
inline void operator()(const IterT& iter) { getValue(iter, hist); }
// Accumulate another functor's Histogram object into this functor's.
inline void join(HistOp& other) { hist.add(other.hist); }
math::Histogram hist;
ValueOp getValue;
};
// Helper class to apply an operator such as math::Gradient or math::Laplacian
// to voxels and accumulate the scalar results or the magnitudes of vector results
// into a math::Stats object
template<typename IterT, typename OpT, typename StatsT>
struct MathOp
{
using TreeT = typename IterT::TreeT;
using ValueT = typename TreeT::ValueType;
using ConstAccessor = typename tree::ValueAccessor<const TreeT>;
// Each thread gets its own accessor and its own copy of the operator.
ConstAccessor mAcc;
OpT mOp;
StatsT mStats;
template<typename TreeT>
static inline TreeT* THROW_IF_NULL(TreeT* ptr) {
if (ptr == nullptr) OPENVDB_THROW(ValueError, "iterator references a null tree");
return ptr;
}
MathOp(const IterT& iter, const OpT& op):
mAcc(*THROW_IF_NULL(iter.getTree())), mOp(op)
{}
// Accumulate voxel and tile values into this functor's Stats object.
void operator()(const IterT& it)
{
if (it.isVoxelValue()) {
// Add the magnitude of the gradient at a single voxel.
mStats.add(mOp.result(mAcc, it.getCoord()));
} else {
// Iterate over the voxels enclosed by a tile and add the results
// of applying the operator at each voxel.
/// @todo This could be specialized to be done more efficiently for some operators.
/// For example, all voxels in the interior of a tile (i.e., not on the borders)
/// have gradient zero, so there's no need to apply the operator to every voxel.
CoordBBox bbox = it.getBoundingBox();
Coord xyz;
int &x = xyz.x(), &y = xyz.y(), &z = xyz.z();
for (x = bbox.min().x(); x <= bbox.max().x(); ++x) {
for (y = bbox.min().y(); y <= bbox.max().y(); ++y) {
for (z = bbox.min().z(); z <= bbox.max().z(); ++z) {
mStats.add(mOp.result(mAcc, it.getCoord()));
}
}
}
}
}
// Accumulate another functor's Stats object into this functor's.
inline void join(MathOp& other) { mStats.add(other.mStats); }
}; // struct MathOp
} // namespace stats_internal
/// @endcond
template<typename IterT>
inline math::Histogram
histogram(const IterT& iter, double vmin, double vmax, size_t numBins, bool threaded)
{
using ValueOp = stats_internal::GetVal<IterT, math::Histogram>;
ValueOp valOp;
stats_internal::HistOp<IterT, ValueOp> op(valOp, vmin, vmax, numBins);
tools::accumulate(iter, op, threaded);
return op.hist;
}
template<typename IterT>
inline math::Extrema
extrema(const IterT& iter, bool threaded)
{
stats_internal::GetVal<IterT, math::Extrema> valOp;
return extrema(iter, valOp, threaded);
}
template<typename IterT>
inline math::Stats
statistics(const IterT& iter, bool threaded)
{
stats_internal::GetVal<IterT, math::Stats> valOp;
return statistics(iter, valOp, threaded);
}
template<typename IterT, typename ValueOp>
inline math::Extrema
extrema(const IterT& iter, const ValueOp& valOp, bool threaded)
{
stats_internal::StatsOp<IterT, const ValueOp, math::Extrema> op(valOp);
tools::accumulate(iter, op, threaded);
return op.stats;
}
template<typename IterT, typename ValueOp>
inline math::Stats
statistics(const IterT& iter, const ValueOp& valOp, bool threaded)
{
stats_internal::StatsOp<IterT, const ValueOp, math::Stats> op(valOp);
tools::accumulate(iter, op, threaded);
return op.stats;
}
template<typename OperatorT, typename IterT>
inline math::Extrema
opExtrema(const IterT& iter, const OperatorT& op, bool threaded)
{
stats_internal::MathOp<IterT, OperatorT, math::Extrema> func(iter, op);
tools::accumulate(iter, func, threaded);
return func.mStats;
}
template<typename OperatorT, typename IterT>
inline math::Stats
opStatistics(const IterT& iter, const OperatorT& op, bool threaded)
{
stats_internal::MathOp<IterT, OperatorT, math::Stats> func(iter, op);
tools::accumulate(iter, func, threaded);
return func.mStats;
}
} // namespace tools
} // namespace OPENVDB_VERSION_NAME
} // namespace openvdb
#endif // OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
Stats.h
Classes to compute statistics and histograms.
ValueTransformer.h
openvdb::v10_0::math::Extrema
This class computes the minimum and maximum values of a population of floating-point values.
Definition Stats.h:93
openvdb::v10_0::math::Stats
This class computes statistics (minimum value, maximum value, mean, variance and standard deviation) ...
Definition Stats.h:183
nanovdb::CoordBBox
BBox< Coord > CoordBBox
Definition NanoVDB.h:1809
openvdb::v10_0::tools::statistics
math::Stats statistics(const IterT &iter, bool threaded=true)
Iterate over a scalar grid and compute statistics (mean, variance, etc.) of the values of the voxels ...
Definition Statistics.h:362
openvdb::v10_0::tools::opStatistics
math::Stats opStatistics(const IterT &iter, const OperatorT &op=OperatorT(), bool threaded=true)
Iterate over a grid and compute statistics (mean, variance, etc.) of the values produced by applying ...
Definition Statistics.h:398
openvdb::v10_0::tools::histogram
math::Histogram histogram(const IterT &iter, double minVal, double maxVal, size_t numBins=10, bool threaded=true)
Iterate over a scalar grid and compute a histogram of the values of the voxels that are visited,...
Definition Statistics.h:343
openvdb::v10_0::tools::accumulate
void accumulate(const IterT &iter, XformOp &op, bool threaded=true)
Definition ValueTransformer.h:679
openvdb::v10_0::tools::opExtrema
math::Extrema opExtrema(const IterT &iter, const OperatorT &op=OperatorT(), bool threaded=true)
Same as opStatistics except it returns a math::Extrema vs a math::Stats.
Definition Statistics.h:389
openvdb::v10_0::tools::extrema
math::Extrema extrema(const IterT &iter, bool threaded=true)
Iterate over a scalar grid and compute extrema (min/max) of the values of the voxels that are visited...
Definition Statistics.h:354
openvdb
Definition Exceptions.h:13
Exceptions.h
OPENVDB_THROW
#define OPENVDB_THROW(exception, message)
Definition Exceptions.h:74
Types.h
OPENVDB_VERSION_NAME
#define OPENVDB_VERSION_NAME
The version namespace name for this library version.
Definition version.h.in:121
OPENVDB_USE_VERSION_NAMESPACE
#define OPENVDB_USE_VERSION_NAMESPACE
Definition version.h.in:212