c – 具有整数矩阵MxN如何将它们分组为具有增强几何的多边形?
作者:互联网
我们有一个给定整数的矩阵(从1到INT_MAX),如
1 2 3
1 3 3
1 3 3
100 2 1
我们想为矩阵中的每个唯一int创建具有相同颜色的多边形,因此我们的多边形将具有如此处所示的坐标/分组.
我们可以像这样生成图像:
哪个*(因为执行的vectirisation将扩展到如此大小):
(抱歉蹩脚的图纸)
是否有可能以及如何使用提升几何来做这样的事情?
更新:
所以@sehe sad: I'd simply let Boost Geometry do most of the work.
所以我创建了this像素类aeria种植者使用纯粹的Boost.Geometry,编译,运行但我需要它在集群数据上运行..我有1000个1800个文件的uchars(每个独特的uchar ==数据属于那个claster).这段代码的问题:在第18行,它变得很慢,每个点创建开始花费超过一秒=(
码:
//Boost
#include <boost/assign.hpp>
#include <boost/foreach.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
#include <boost/geometry/geometries/adapted/boost_tuple.hpp>
//and this is why we use Boost Geometry from Boost trunk
//#include <boost/geometry/extensions/io/svg/svg_mapper.hpp>
BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)
void make_point(int x, int y, boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > & ring)
{
using namespace boost::assign;
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y-1));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x, y-1));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x, y));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y-1));
boost::geometry::correct(ring);
}
void create_point(int x, int y, boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > & mp)
{
boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > temp;
boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > ring;
make_point(x, y, ring);
boost::geometry::union_(mp, ring, temp);
boost::geometry::correct(temp);
mp=temp;
}
int main()
{
using namespace boost::assign;
boost::geometry::model::multi_polygon< boost::geometry::model::polygon < boost::geometry::model::d2::point_xy<double> > > pol, simpl;
//read image
std::ifstream in("1.mask", std::ios_base::in | std::ios_base::binary);
int sx, sy;
in.read(reinterpret_cast<char*>(&sy), sizeof(int));
in.read(reinterpret_cast<char*>(&sx), sizeof(int));
std::vector< std::vector<unsigned char> > image(sy);
for(int i =1; i <= sy; i++)
{
std::vector<unsigned char> row(sx);
in.read(reinterpret_cast<char*>(&row[0]), sx);
image[i-1] = row;
}
//
std::map<unsigned char, boost::geometry::model::multi_polygon < boost::geometry::model::polygon < boost::geometry::model::d2::point_xy<double> > > > layered_image;
for(int y=1; y <= sy; y++)
{
for(int x=1; x <= sx; x++)
{
if (image[y-1][x-1] != 1)
{
create_point(x, y, layered_image[image[y-1][x-1]]);
std::cout << x << " : " << y << std::endl;
}
}
}
}
所以你可以看到我的代码很糟糕..所以我决定为@sehe code创建一个渲染器:
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <set>
//Boost
#include <boost/assign.hpp>
#include <boost/array.hpp>
#include <boost/algorithm/string.hpp>
#include <boost/geometry/geometry.hpp>
#include <boost/geometry/geometries/geometries.hpp>
#include <boost/geometry/multi/geometries/multi_polygon.hpp>
#include <boost/geometry/geometries/adapted/boost_tuple.hpp>
#include <boost/random/uniform_int.hpp>
#include <boost/random/mersenne_twister.hpp>
//and this is why we use Boost Geometry from Boost trunk
#include <boost/geometry/extensions/io/svg/svg_mapper.hpp>
BOOST_GEOMETRY_REGISTER_BOOST_TUPLE_CS(cs::cartesian)
namespace mxdetail
{
typedef size_t cell_id; // row * COLS + col
template <typename T> struct area
{
T value;
typedef std::vector<cell_id> cells_t;
cells_t cells;
};
template <typename T, size_t Rows, size_t Cols>
std::vector<area<T> > getareas(const boost::array<boost::array<T, Cols>, Rows>& matrix)
{
typedef boost::array<boost::array<T, Cols>, Rows> mtx;
std::vector<area<T> > areas;
struct visitor_t
{
const mtx& matrix;
std::set<cell_id> visited;
visitor_t(const mtx& mtx) : matrix(mtx) { }
area<T> start(const int row, const int col)
{
area<T> result;
visit(row, col, result);
return result;
}
void visit(const int row, const int col, area<T>& current)
{
const cell_id id = row*Cols+col;
if (visited.end() != visited.find(id))
return;
bool matches = current.cells.empty() || (matrix[row][col] == current.value);
if (matches)
{
visited.insert(id);
current.value = matrix[row][col];
current.cells.push_back(id);
// process neighbours
for (int nrow=std::max(0, row-1); nrow < std::min((int) Rows, row+2); nrow++)
for (int ncol=std::max(0, col-1); ncol < std::min((int) Cols, col+2); ncol++)
/* if (ncol!=col || nrow!=row) */
visit(nrow, ncol, current);
}
}
} visitor(matrix);
for (int r=0; r < (int) Rows; r++)
for (int c=0; c < (int) Cols; c++)
{
mxdetail::area<int> area = visitor.start(r,c);
if (!area.cells.empty()) // happens when startpoint already visited
areas.push_back(area);
}
return areas;
}
}
typedef boost::array<int, 4> row;
template <typename T, size_t N>
boost::array<T, N> make_array(const T (&a)[N])
{
boost::array<T, N> result;
std::copy(a, a+N, result.begin());
return result;
}
void make_point(int x, int y, boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > & ring)
{
using namespace boost::assign;
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y-1));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x, y-1));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x, y));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y));
boost::geometry::append( ring, boost::geometry::model::d2::point_xy<double>(x-1, y-1));
boost::geometry::correct(ring);
}
void create_point(int x, int y, boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > & mp)
{
boost::geometry::model::multi_polygon< boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > > temp;
boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > ring;
make_point(x, y, ring);
boost::geometry::union_(mp, ring, temp);
boost::geometry::correct(temp);
mp=temp;
}
boost::random::mt19937 rng;
boost::random::uniform_int_distribution<> color(10,255);
std::string fill_rule()
{
int red, green, blue;
red = color(rng);
green = color(rng);
blue = color(rng);
std::ostringstream rule;
rule << "fill-rule:nonzero;fill-opacity:0.5;fill:rgb("
<< red << "," << green << "," << blue
<< ");stroke:rgb("
<< (red - 5) << "," << (green - 5) << "," << (blue -5)
<< ");stroke-width:2";
return rule.str();
}
int main()
{
int sx = 4;
int sy = 5;
int row0[] = { 1 , 2, 3, 3, };
int row1[] = { 1 , 3, 3, 3,};
int row2[] = { 1 , 3, 3, 3, };
int row3[] = { 2 , 2, 1, 2, };
int row4[] = { 100, 2, 2, 2, };
boost::array<row, 5> matrix;
matrix[0] = make_array(row0);
matrix[1] = make_array(row1);
matrix[2] = make_array(row2);
matrix[3] = make_array(row3);
matrix[4] = make_array(row4);
typedef std::vector<mxdetail::area<int> > areas_t;
typedef areas_t::value_type::cells_t cells_t;
areas_t areas = mxdetail::getareas(matrix);
using namespace boost::assign;
typedef boost::geometry::model::polygon
<
boost::geometry::model::d2::point_xy<double>
> polygon;
typedef boost::geometry::model::multi_polygon<polygon> mp;
typedef boost::geometry::point_type<mp>::type point_type;
std::string filename = "draw.svg";
std::ofstream svg(filename.c_str());
boost::geometry::svg_mapper<point_type> mapper(svg, 400, 400);
for (areas_t::const_iterator it=areas.begin(); it!=areas.end(); ++it)
{
mp pol;
std::cout << "area of " << it->value << ": ";
for (cells_t::const_iterator pit=it->cells.begin(); pit!=it->cells.end(); ++pit)
{
int row = *pit / 3, col = *pit % 3;
std::cout << "(" << row << "," << col << "), ";
create_point( (row+1), (col+1), pol);
}
std::cout << std::endl;
mapper.add(pol);
mapper.map(pol, fill_rule());
}
std::cout << "areas detected: " << areas.size() << std::endl;
std::cin.get();
}
这段代码是可编译的,但它很糟糕(似乎我毕竟没有得到如何处理数组…):
解决方法:
简而言之,如果我的问题是正确的,我只需让Boost Geometry完成大部分工作.
对于NxM的样本矩阵,创建NxM’flyweight’矩形多边形以在视觉上对应于每个矩阵单元.
现在,使用迭代深化算法,找到所有组:
* for each _unvisited_ cell in matrix
* start a new group
* [visit:]
- mark _visited_
- for each neighbour with equal value:
- add to curent group and
- recurse [visit:]
请注意,此算法的结果可能是具有相同值的不同组(表示析取多边形).例如.来自OP中样本的值2将导致两组.
现在,对于每个组,只需调用Boost Geometry’s Union_
algorithm以查找表示该组的合并多边形.
示例实施
更新此处是C 11中的非优化实现:
编辑请参阅此处获取C++03 version (using Boost)
测试中使用的样本数据对应于问题中的矩阵.
#include <iostream>
#include <array>
#include <vector>
#include <set>
namespace mxdetail
{
typedef size_t cell_id; // row * COLS + col
template <typename T> struct area
{
T value;
std::vector<cell_id> cells;
};
template <typename T, size_t Rows, size_t Cols>
std::vector<area<T> > getareas(const std::array<std::array<T, Cols>, Rows>& matrix)
{
typedef std::array<std::array<T, Cols>, Rows> mtx;
std::vector<area<T> > areas;
struct visitor_t
{
const mtx& matrix;
std::set<cell_id> visited;
visitor_t(const mtx& mtx) : matrix(mtx) { }
area<T> start(const int row, const int col)
{
area<T> result;
visit(row, col, result);
return result;
}
void visit(const int row, const int col, area<T>& current)
{
const cell_id id = row*Cols+col;
if (visited.end() != visited.find(id))
return;
bool matches = current.cells.empty() || (matrix[row][col] == current.value);
if (matches)
{
visited.insert(id);
current.value = matrix[row][col];
current.cells.push_back(id);
// process neighbours
for (int nrow=std::max(0, row-1); nrow < std::min((int) Rows, row+2); nrow++)
for (int ncol=std::max(0, col-1); ncol < std::min((int) Cols, col+2); ncol++)
/* if (ncol!=col || nrow!=row) */
visit(nrow, ncol, current);
}
}
} visitor(matrix);
for (int r=0; r < Rows; r++)
for (int c=0; c < Cols; c++)
{
auto area = visitor.start(r,c);
if (!area.cells.empty()) // happens when startpoint already visited
areas.push_back(area);
}
return areas;
}
}
int main()
{
typedef std::array<int, 3> row;
std::array<row, 4> matrix = {
row { 1 , 2, 3, },
row { 1 , 3, 3, },
row { 1 , 3, 3, },
row { 100, 2, 1, },
};
auto areas = mxdetail::getareas(matrix);
std::cout << "areas detected: " << areas.size() << std::endl;
for (const auto& area : areas)
{
std::cout << "area of " << area.value << ": ";
for (auto pt : area.cells)
{
int row = pt / 3, col = pt % 3;
std::cout << "(" << row << "," << col << "), ";
}
std::cout << std::endl;
}
}
用gcc-4.6 -std = c 0x编译输出为:
areas detected: 6
area of 1: (0,0), (1,0), (2,0),
area of 2: (0,1),
area of 3: (0,2), (1,1), (1,2), (2,1), (2,2),
area of 100: (3,0),
area of 2: (3,1),
area of 1: (3,2),
标签:boost-geometry,c,vector,boost,vector-graphics 来源: https://codeday.me/bug/20191008/1872657.html