Boost联合在1.67中无效,但在1.61中有效。为什么?

时间:2018-07-22 15:45:35

标签: c++ boost geometry union boost-geometry

我正在尝试弄清为什么我的以下代码在boost 1.61中可以正常工作,而在boost 1.67中却不能正常工作。

boost 1.61中,正确组合了输入多边形并显示了轮廓多边形。

boost 1.67中,没有代码更改,轮廓多边形是错误且不完整。好像它缺少点。

已添加输出图像以帮助说明。我还需要添加一个#define BOOST_1_6_1,因为boost 1.61似乎并没有自动添加该头文件。

如果要查看输入多边形的外观,请取消注释drawAllPolygons()

有人可以帮忙吗?

#include <iostream>


#include <boost\geometry.hpp>

//#define BOOST_1_6_1
#ifdef BOOST_1_6_1
#include <boost/geometry/geometries/point_xy.hpp>
#endif

typedef boost::geometry::model::d2::point_xy<int> intPt;
typedef boost::geometry::model::polygon<intPt> polygon;

const int GRID_WIDTH = 220;
const int GRID_HEIGHT = 60;

bool canvas[GRID_WIDTH][GRID_HEIGHT];

std::vector<polygon> output;
std::vector<polygon> input;

void initCanvas()
{
    for (unsigned int y = 0; y < GRID_HEIGHT; ++y)
    {
        for (unsigned int x = 0; x < GRID_WIDTH; ++x)
        {
            canvas[x][y] = false;
        }
    }
}

void drawGrid()
{
    for (unsigned int y = 0; y < GRID_HEIGHT; ++y)
    {
        for (unsigned int x = 0; x < GRID_WIDTH; ++x)
        {
            if (canvas[x][y])
            {
                std::cout << "x";
            } 
            else
            {
                std::cout << ".";
            }
        }

        std::cout << std::endl;
    }
}

polygon setupPolygon(const int startX, const int startY, const int width, const int height)
{
    polygon polygon1;

    int endX = startX + width;
    int endY = startY + height;

    for (int x = startX; x <= endX; ++x)
    {
        intPt pt(x, startY);
        polygon1.outer().push_back(pt);
    }

    for (int y = startY; y <= endY; ++y)
    {
        intPt pt(endX, y);
        polygon1.outer().push_back(pt);
    }

    for (int x = endX; x >= startX; --x)
    {
        intPt pt(x, endY);
        polygon1.outer().push_back(pt);
    }

    for (int y = endY; y >= startY; --y)
    {
        intPt pt(startX, y);
        polygon1.outer().push_back(pt);
    }

    return polygon1;
}

std::vector<polygon> combine(std::vector<polygon> input)
{
    bool loop = true;
    while (loop)
    {
        unsigned int before = input.size();
        bool exit = false;
        for (unsigned int i = 0; i < input.size() && !exit; ++i)
        {
            for (unsigned int j = i + 1; j < input.size() && !exit; ++j)
            {
                std::vector<polygon> output;
                boost::geometry::correct(input[i]);
                boost::geometry::correct(input[j]);
                boost::geometry::union_(input[i], input[j], output);

                if (i < j)
                { 
                    input.erase(input.begin() + j);
                    input.erase(input.begin() + i);
                }
                else
                {
                    input.erase(input.begin() + i);
                    input.erase(input.begin() + j);
                }

                input.insert(input.begin(), output.begin(), output.end());

                exit = true;
            }
        }

        if (before == input.size())
        {
            loop = false;
        }
    }


    return input;
}

void drawAllPolygons()
{
    for (unsigned int i = 0; i < input.size(); ++i)
    {
        auto outer = input[i].outer();
        for (unsigned int i = 0; i < outer.size(); ++i)
        {
            int x = outer[i].get<0>();
            int y = outer[i].get<1>();
            canvas[x][y] = true;
        }
    }
}

void drawCombinedPolygons()
{
    for (unsigned int j = 0; j < output.size(); ++j)
    {
        auto outer = output[j].outer();
        for (unsigned int i = 0; i < outer.size(); ++i)
        {
            int x = outer[i].get<0>();
            int y = outer[i].get<1>();
            canvas[x][y] = true;
        }
    }
}

int main()
{
    initCanvas();

    input.push_back(setupPolygon(40, 10, 50, 15));
    input.push_back(setupPolygon(40, 20, 50, 15));
    input.push_back(setupPolygon(50, 10, 50, 15));
    input.push_back(setupPolygon(60, 30, 50, 15));

    output = combine(input);

    //drawAllPolygons();
    drawCombinedPolygons();

    drawGrid();

    std::cin.get();

    return 0;
}

enter image description here enter image description here

1 个答案:

答案 0 :(得分:2)

Boost 1.61显然并未进行所有可能的优化。


有很多误解。

  1. 输入多边形(环)的方向错误。您可以使用is_validcorrect来帮助自己。下面的代码将显示它。

  2. 明确地创建了原始多边形,以包含许多冗余点。即使您只是与其中一个“联合”,您也可以期望结果得到简化:

    Live On Coliru

    polygon p = setupPolygon(40, 10, 50, 15);
    std::cout << "original: " << bg::wkt(p) << "\n";
    multi_polygon simple;
    bg::union_(p, p, simple);
    std::cout << "self-union: " << bg::wkt(simple) << "\n";
    

    将打印

    original: POLYGON((40 10,40 11,40 12,40 13,40 14,40 15,40 16,40 17,40 18,40 19,40 20,40 21,40 22,40 23,40 24,40 25,40 25,41 25,42 25,43 25,44 25,45 25,46 25,47 25,48 25,49 25,50 25,51 25,52 25,53 25,54 25,55 25,56 25,57 25,58 25,59 25,60 25,61 25,62 25,63 25,64 25,65 25,66 25,67 25,68 25,69 25,70 25,71 25,72 25,73 25,74 25,75 25,76 25,77 25,78 25,79 25,80 25,81 25,82 25,83 25,84 25,85 25,86 25,87 25,88 25,89 25,90 25,90 25,90 24,90 23,90 22,90 21,90 20,90 19,90 18,90 17,90 16,90 15,90 14,90 13,90 12,90 11,90 10,90 10,89 10,88 10,87 10,86 10,85 10,84 10,83 10,82 10,81 10,80 10,79 10,78 10,77 10,76 10,75 10,74 10,73 10,72 10,71 10,70 10,69 10,68 10,67 10,66 10,65 10,64 10,63 10,62 10,61 10,60 10,59 10,58 10,57 10,56 10,55 10,54 10,53 10,52 10,51 10,50 10,49 10,48 10,47 10,46 10,45 10,44 10,43 10,42 10,41 10,40 10))
    self-union: MULTIPOLYGON(((90 25,90 10,40 10,40 25,90 25)))
    

    如您所见,结果将简化为矩形的明显角。但是,您的“绘图”代码依赖于要显示的多余点

    这就是为什么您最终得到“斑点”结果的原因-似乎遗漏了点,仅是因为您的绘制代码没有绘制任何线条。它只是画出(角)点。

  3. canvas的尺寸倒置

    认为,您的canvas索引一直在交换。我建议使用更明确的数据结构进行(可选)边界检查来避免这种情况。

更改为使用SVG

如果更改代码以输出输入和输出的SVG,您会发现整个过程都很合理。请注意,这也要注意纠正输入:

Live On Coliru

#include <iostream>
#include <fstream>

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>

namespace bg = boost::geometry;
typedef bg::model::d2::point_xy<int> intPt;
typedef bg::model::polygon<intPt> polygon;
typedef bg::model::multi_polygon<polygon> multi_polygon;

const int GRID_WIDTH = 220;
const int GRID_HEIGHT = 60;

std::array<std::array<bool, GRID_WIDTH>, GRID_HEIGHT> canvas;

void initCanvas() {
    for (auto& row : canvas)
        for (auto& cell : row)
            cell = false;
}

void drawGrid() {
    for (auto& row : canvas) {
        for (auto& cell : row)
            std::cout << (cell?"x":".");
        std::cout << std::endl;
    }
}

template <typename R> void valid(R& g) {
    std::string reason;
    while (!bg::is_valid(g, reason)) {
        std::cout << "Not valid: " << reason << "\n";
        bg::correct(g);
    }
}

polygon setupPolygon(const int startX, const int startY, const int width, const int height) {
    polygon::ring_type r;

    int const endX = startX + width;
    int const endY = startY + height;

    for (int x = startX; x <= endX;   ++x) r.emplace_back(x,      startY);
    for (int y = startY; y <= endY;   ++y) r.emplace_back(endX,   y);
    for (int x = endX;   x >= startX; --x) r.emplace_back(x,      endY);
    for (int y = endY;   y >= startY; --y) r.emplace_back(startX, y);

    valid(r);

    return {r};
}

template <typename Polygons>
multi_polygon combine(Polygons const& input) {

    if (input.empty()) return {};
    //if (input.size()<2) return {input.front()};

    multi_polygon out;
    for (polygon const& i : input) {
        multi_polygon tmp;
        bg::union_(out, i, tmp);
        out = tmp;
    }

    return out;
}

void draw(polygon const& p) {
    for (auto& pt : p.outer())
        canvas.at(pt.y()).at(pt.x()) = true;
}

void draw(multi_polygon const& mp) { for (auto& p : mp) draw(p); }
void draw(std::vector<polygon> const& mp) { for (auto& p : mp) draw(p); }

void writeSvg(multi_polygon const& g, std::string fname) {
    std::ofstream svg(fname);
    boost::geometry::svg_mapper<intPt> mapper(svg, 400, 400);
    mapper.add(g);
    mapper.map(g, "fill-opacity:0.5;fill:rgb(0,0,153);stroke:rgb(0,0,200);stroke-width:2");
}

void writeSvg(std::vector<polygon> const& g, std::string fname) {
    std::ofstream svg(fname);
    boost::geometry::svg_mapper<intPt> mapper(svg, 400, 400);
    for (auto& p: g) {
        mapper.add(p);
        mapper.map(p, "fill-opacity:0.5;fill:rgb(153,0,0);stroke:rgb(200,0,0);stroke-width:2");
    }
}

int main() {
    std::vector<polygon> input { {
        setupPolygon(40, 10, 50, 15),
        setupPolygon(40, 20, 50, 15),
        setupPolygon(50, 10, 50, 15),
        setupPolygon(60, 30, 50, 15),
    } };

    for (auto& p : input)
        valid(p);

    auto output = combine(input);

    initCanvas();
    draw(input);
    drawGrid();

    initCanvas();
    draw(output);
    drawGrid();

    writeSvg(input, "input.svg");
    writeSvg(output, "output.svg");
}

打印

Not valid: Geometry has wrong orientation
Not valid: Geometry has wrong orientation
Not valid: Geometry has wrong orientation
Not valid: Geometry has wrong orientation
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........................................xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.......................................................................................................................
........................................x.........x.......................................x.........x.......................................................................................................................
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........................................x.........x.......................................x.........x.......................................................................................................................
[ snip ]
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和input.svg:

enter image description here

和output.svg:

enter image description here