/usr/include/boost/geometry/strategies/agnostic/hull_graham_andrew.hpp is in libboost1.55-dev 1.55.0+dfsg-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 | // Boost.Geometry (aka GGL, Generic Geometry Library)
// Copyright (c) 2007-2012 Barend Gehrels, Amsterdam, the Netherlands.
// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
// Use, modification and distribution is subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_CONVEX_GRAHAM_ANDREW_HPP
#define BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_CONVEX_GRAHAM_ANDREW_HPP
#include <cstddef>
#include <algorithm>
#include <vector>
#include <boost/range.hpp>
#include <boost/geometry/core/cs.hpp>
#include <boost/geometry/core/point_type.hpp>
#include <boost/geometry/strategies/convex_hull.hpp>
#include <boost/geometry/views/detail/range_type.hpp>
#include <boost/geometry/policies/compare.hpp>
#include <boost/geometry/algorithms/detail/for_each_range.hpp>
#include <boost/geometry/views/reversible_view.hpp>
namespace boost { namespace geometry
{
namespace strategy { namespace convex_hull
{
#ifndef DOXYGEN_NO_DETAIL
namespace detail
{
template
<
typename InputRange,
typename RangeIterator,
typename StrategyLess,
typename StrategyGreater
>
struct get_extremes
{
typedef typename point_type<InputRange>::type point_type;
point_type left, right;
bool first;
StrategyLess less;
StrategyGreater greater;
inline get_extremes()
: first(true)
{}
inline void apply(InputRange const& range)
{
if (boost::size(range) == 0)
{
return;
}
// First iterate through this range
// (this two-stage approach avoids many point copies,
// because iterators are kept in memory. Because iterators are
// not persistent (in MSVC) this approach is not applicable
// for more ranges together)
RangeIterator left_it = boost::begin(range);
RangeIterator right_it = boost::begin(range);
for (RangeIterator it = boost::begin(range) + 1;
it != boost::end(range);
++it)
{
if (less(*it, *left_it))
{
left_it = it;
}
if (greater(*it, *right_it))
{
right_it = it;
}
}
// Then compare with earlier
if (first)
{
// First time, assign left/right
left = *left_it;
right = *right_it;
first = false;
}
else
{
// Next time, check if this range was left/right from
// the extremes already collected
if (less(*left_it, left))
{
left = *left_it;
}
if (greater(*right_it, right))
{
right = *right_it;
}
}
}
};
template
<
typename InputRange,
typename RangeIterator,
typename Container,
typename SideStrategy
>
struct assign_range
{
Container lower_points, upper_points;
typedef typename point_type<InputRange>::type point_type;
point_type const& most_left;
point_type const& most_right;
inline assign_range(point_type const& left, point_type const& right)
: most_left(left)
, most_right(right)
{}
inline void apply(InputRange const& range)
{
typedef SideStrategy side;
// Put points in one of the two output sequences
for (RangeIterator it = boost::begin(range);
it != boost::end(range);
++it)
{
// check if it is lying most_left or most_right from the line
int dir = side::apply(most_left, most_right, *it);
switch(dir)
{
case 1 : // left side
upper_points.push_back(*it);
break;
case -1 : // right side
lower_points.push_back(*it);
break;
// 0: on line most_left-most_right,
// or most_left, or most_right,
// -> all never part of hull
}
}
}
};
template <typename Range>
static inline void sort(Range& range)
{
typedef typename boost::range_value<Range>::type point_type;
typedef geometry::less<point_type> comparator;
std::sort(boost::begin(range), boost::end(range), comparator());
}
} // namespace detail
#endif // DOXYGEN_NO_DETAIL
/*!
\brief Graham scan strategy to calculate convex hull
\ingroup strategies
\note Completely reworked version inspired on the sources listed below
\see http://www.ddj.com/architect/201806315
\see http://marknelson.us/2007/08/22/convex
*/
template <typename InputGeometry, typename OutputPoint>
class graham_andrew
{
public :
typedef OutputPoint point_type;
typedef InputGeometry geometry_type;
private:
typedef typename cs_tag<point_type>::type cs_tag;
typedef typename std::vector<point_type> container_type;
typedef typename std::vector<point_type>::const_iterator iterator;
typedef typename std::vector<point_type>::const_reverse_iterator rev_iterator;
class partitions
{
friend class graham_andrew;
container_type m_lower_hull;
container_type m_upper_hull;
container_type m_copied_input;
};
public:
typedef partitions state_type;
inline void apply(InputGeometry const& geometry, partitions& state) const
{
// First pass.
// Get min/max (in most cases left / right) points
// This makes use of the geometry::less/greater predicates
// For the left boundary it is important that multiple points
// are sorted from bottom to top. Therefore the less predicate
// does not take the x-only template parameter (this fixes ticket #6019.
// For the right boundary it is not necessary (though also not harmful),
// because points are sorted from bottom to top in a later stage.
// For symmetry and to get often more balanced lower/upper halves
// we keep it.
typedef typename geometry::detail::range_type<InputGeometry>::type range_type;
typedef typename boost::range_iterator
<
range_type const
>::type range_iterator;
detail::get_extremes
<
range_type,
range_iterator,
geometry::less<point_type>,
geometry::greater<point_type>
> extremes;
geometry::detail::for_each_range(geometry, extremes);
// Bounding left/right points
// Second pass, now that extremes are found, assign all points
// in either lower, either upper
detail::assign_range
<
range_type,
range_iterator,
container_type,
typename strategy::side::services::default_strategy<cs_tag>::type
> assigner(extremes.left, extremes.right);
geometry::detail::for_each_range(geometry, assigner);
// Sort both collections, first on x(, then on y)
detail::sort(assigner.lower_points);
detail::sort(assigner.upper_points);
//std::cout << boost::size(assigner.lower_points) << std::endl;
//std::cout << boost::size(assigner.upper_points) << std::endl;
// And decide which point should be in the final hull
build_half_hull<-1>(assigner.lower_points, state.m_lower_hull,
extremes.left, extremes.right);
build_half_hull<1>(assigner.upper_points, state.m_upper_hull,
extremes.left, extremes.right);
}
template <typename OutputIterator>
inline void result(partitions const& state,
OutputIterator out, bool clockwise) const
{
if (clockwise)
{
output_range<iterate_forward>(state.m_upper_hull, out, false);
output_range<iterate_reverse>(state.m_lower_hull, out, true);
}
else
{
output_range<iterate_forward>(state.m_lower_hull, out, false);
output_range<iterate_reverse>(state.m_upper_hull, out, true);
}
}
private:
template <int Factor>
static inline void build_half_hull(container_type const& input,
container_type& output,
point_type const& left, point_type const& right)
{
output.push_back(left);
for(iterator it = input.begin(); it != input.end(); ++it)
{
add_to_hull<Factor>(*it, output);
}
add_to_hull<Factor>(right, output);
}
template <int Factor>
static inline void add_to_hull(point_type const& p, container_type& output)
{
typedef typename strategy::side::services::default_strategy<cs_tag>::type side;
output.push_back(p);
register std::size_t output_size = output.size();
while (output_size >= 3)
{
rev_iterator rit = output.rbegin();
point_type const& last = *rit++;
point_type const& last2 = *rit++;
if (Factor * side::apply(*rit, last, last2) <= 0)
{
// Remove last two points from stack, and add last again
// This is much faster then erasing the one but last.
output.pop_back();
output.pop_back();
output.push_back(last);
output_size--;
}
else
{
return;
}
}
}
template <iterate_direction Direction, typename OutputIterator>
static inline void output_range(container_type const& range,
OutputIterator out, bool skip_first)
{
typedef typename reversible_view<container_type const, Direction>::type view_type;
view_type view(range);
bool first = true;
for (typename boost::range_iterator<view_type const>::type it = boost::begin(view);
it != boost::end(view); ++it)
{
if (first && skip_first)
{
first = false;
}
else
{
*out = *it;
++out;
}
}
}
};
}} // namespace strategy::convex_hull
#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
template <typename InputGeometry, typename OutputPoint>
struct strategy_convex_hull<InputGeometry, OutputPoint, cartesian_tag>
{
typedef strategy::convex_hull::graham_andrew<InputGeometry, OutputPoint> type;
};
#endif
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_STRATEGIES_AGNOSTIC_CONVEX_GRAHAM_ANDREW_HPP
|