Boost :: geometry :: multi_polygonの負のバッファ

Question

Boost :: geometryを使用してマルチポリゴンに負のバッファを適用しようとしました。以下のコードを実行すると、適切な結果が得られます。しかし、WKTのジオメトリをエクスポートして再インポートしたマークされたブロックを削除すると、tmp_erosionジオメトリに空のMultiPolygonが表示されます。 boost :: geometry :: correct（）関数を使用しようとしましたが、何も変更されません。それを修正する方法はありますか？ また、ジオメトリをWKBにエクスポートしようとしましたが、export-then-import-WKTの前後でジオメトリが異なります。私はそれが何らかの丸め操作のためにどこかにあると思う、それは私の問題に関連することができますか？

std::string wkt = "MULTIPOLYGON(((-203.3984972480392 326.87043766411114,-234.3294031269611 350.72117460025004,-234.32940582512484 350.7211767561067,-234.59541944833873 350.9413566745228,-234.5954246133754 350.9413612592119,-234.8456066177885 351.1793768235705,-234.84561145406377 351.179381753826,-235.078768547128 351.43409770182103,-235.07877303157431 351.43410295412707,-235.29379312442313 351.70430436766964,-235.29379723565108 351.7043099169743,-235.39951413618792 351.85781786966413,-240.86780715032046 350.38218215855835,-241.2049443604434 350.30361570297174,-241.20495115354115 350.3036143659985,-241.5467165739732 350.24856362767656,-241.54672344329876 350.24856276394,-241.89147886679623 350.21729162130026,-241.89148577942245 350.2172912349408,-242.23758558935015 350.20994967493,-242.58335698974216 350.2265727030494,-242.5833638895166 350.22657327470256,-242.9271563937872 350.26708130353956,-242.92716323747084 350.2670823512364,-243.26732892181855 350.3312812109238,-243.26733567660713 350.3312827296422,-243.60225063542637 350.4188666739157,-243.93029626301933 350.52941192532916,-243.93030274346452 350.52941436202866,-244.24991952642313 350.66239589829064,-244.55956286161836 350.81717054531686,-244.55956894361645 350.81717385333343,-244.8577608930744 350.99300259862656,-244.85776673160544 350.99300631954446,-245.14307795174008 351.18904635131906,-245.1430835188178 351.18905046730254,-245.41415167705114 351.40436658497003,-245.6696669314724 351.6379177381484,-245.66967187701746 351.63792258327567,-245.90841706208894 351.88859631483484,-266.58920031948566 375.16554041806563,-266.58920258870927 375.16554306360825,-266.8114462984894 375.433970996735,-266.8114505535744 375.43397651693255,-267.0144568842047 375.7172330288498,-267.0144607444406 375.7172388320306,-267.19724352509485 376.01394790994334,-267.1972469717292 376.0139539679166,-267.358918274207 376.32267424871253,-267.35892129049665 376.3226805320497,-267.49869574263016 376.6419123042001,-267.4986983139225 376.6419187823777,-267.6158969147833 376.97011127128593,-267.6158990285875 376.970117912834,-267.7099540930073 377.30568358689385,-267.7804054331035 377.6469788117333,-267.780406603398 377.6469856825949,-267.8269143132387 377.99236621139704,-267.8492510917757 378.34014040558645,-267.84925129584775 378.3401473724138,-267.84730904189666 378.68863970288874,-267.8210977526416 379.03614335774023,-267.8210969865306 379.036150285323,-267.7707424635338 379.3809909713855,-267.6964900867632 379.72148658265553,-267.59870274954784 380.0559764307823,-267.5987005618558 380.05598304835985,-267.4778489339802 380.38285544057135,-267.3345253662763 380.7005096185073,-267.334522280147 380.700515867838,-267.1694203712224 381.00741516970913,-267.1694168572867 381.0074211888939,-266.9833347199501 381.3020805089815,-266.77718414040345 381.58305694993714,-266.7771798240608 381.58306242236944,-266.5519583226944 381.8489968074004,-266.5519536356491 381.8490019658822,-266.30875282540296 382.09860488379184,-232.51589024775978 414.4450812583296,-232.51588002802416 414.4450898114167,-232.51586876173633 414.4450969296367,-232.51585664898366 414.445102486571,-232.51584390488657 414.4451063835295,-232.5158373664838 414.445107686701,-211.12681324719696 417.9713206571314,-211.12680695294904 417.97132149052527,-211.1267942693878 417.9713219522357,-211.12678793120457 417.971321578691,-211.1267816295017 417.9713208036793,-211.12676923690148 417.97131806335767,-211.1267572912145 417.97131377541353,-211.12675154646425 417.9713110717222,-177.1106691504801 400.6223337146699,-177.1106636027793 400.62233015463886,-177.11065830167098 400.6223262368518,-177.11064853019522 400.6223173975823,-177.11064000569968 400.62230735032404,-177.11063625823746 400.6223019274713,-177.11063287618194 400.6222962695118,-177.11062726542067 400.6222843475245,-177.11062327082684 400.622271791345,-177.11062190239758 400.6222653432285,-165.59426937600804 335.9234066092942,-162.6596781566315 302.06171116087233,-162.6596788436905 302.0616975137797,-162.65967988463825 302.06169075731424,-162.65968333706937 302.06167753627386,-162.65968573241835 302.0616711334854,-162.6596885596208 302.06166490931287,-162.65969545477958 302.06165311219564,-162.65970389380263 302.0616423651924,-162.65970864407186 302.06163744906183,-162.65971909523134 302.0616286463092,-162.65973064885196 302.0616213504858,-162.65974308921002 302.0616156978157,-162.6597561840252 302.0616117938428,-162.65976290080164 302.0616105217139,-162.65977651628992 302.06160936686865,-162.65979016210093 302.0616100789291,-162.65979691664793 302.06161113225346,-162.65981013134098 302.0616146089008,-162.65982274871268 302.0616198545771,-204.8758528204258 323.10306070098704,-204.8758584840069 323.10306427432,-204.87586903132672 323.1030725164298,-204.87587838335946 323.10308209337154,-204.87588255785658 323.1030873296329,-204.87588981029387 323.1030985804321,-204.8758928557106 323.103104544516,-204.87589549513 323.1031106990528,-204.87589771671574 323.10311701644275,-204.87590086845387 323.1031300258577,-204.87590225445257 323.1031433396602,-204.8759018498778 323.10315671929584,-204.8444560373964 323.42562807154223,-204.84445513319602 323.42563489982314,-204.78751382477697 323.76528940556193,-204.78751245267617 323.76529615540176,-204.70732324106254 324.10023186228716,-204.60427022620226 324.42884648764846,-204.60426794001853 324.4288529850604,-204.47883820282144 324.74959412196023,-204.47883547479194 324.74960044658303,-204.33162256579686 325.0609494910012,-203.3984972480392 326.87043766411114)))"; 

typedef double coordinate_2d; 
typedef boost::geometry::model::d2::point_xy<coordinate_2d> point_2d; 
typedef boost::geometry::model::polygon<point_2d> polygon_2d; 
typedef boost::geometry::model::multi_polygon<polygon_2d> multi_polygon_2d; 
multi_polygon_2d test_erosion, tmp_erosion; 

// Read WKT 
boost::geometry::read_wkt(wkt, test_erosion); 

// Check validity 
std::cout<<boost::geometry::is_valid(test_erosion)<<std::endl; 

////////////////////////////////////////////// 
// WHY DO I NEED THIS BLOCK??? 
////////////////////////////////////////////// 
// Export to wkt 
std::ostringstream tmp_wkt; 
tmp_wkt << boost::geometry::wkt(test_erosion); 

// And read it again 
boost::geometry::read_wkt(tmp_wkt.str(), test_erosion); 
std::cout<<boost::geometry::is_valid(test_erosion)<<std::endl; 
////////////////////////////////////////////// 

// Apply buffer 
boost::geometry::buffer(test_erosion, tmp_erosion, 
    boost::geometry::strategy::buffer::distance_symmetric<double>(-0.00001), 
    boost::geometry::strategy::buffer::side_straight(), 
    boost::geometry::strategy::buffer::join_round(), 
    boost::geometry::strategy::buffer::end_round(), 
    boost::geometry::strategy::buffer::point_circle(360) 
    ); 

// Print result 
std::cout<<boost::geometry::wkt(test_erosion)<<std::endl; 
std::cout<<boost::geometry::wkt(tmp_erosion)<<std::endl; 

Answer 1

しかし、私はマークブロック、単に輸出およびWKTで再インポート ジオメトリを削除した場合、私はtmp_erosion ジオメトリに空のマルチポリゴンを取得します。

tmp_erosionが空の場合はboost::geometry::bufferに何も書き込まれていないためです。

boost::geometry::strategy::buffer::distance_symmetric<double>(-0.00001)が粗すぎるため、何も書かれていないという理由があります。より多くの小数を持つboost::geometry::strategy::buffer::distance_symmetric<double>(-0.0000001)が機能します。

私はどこか

はい、それはあるいくつかの丸め操作によるものであると思います。

std::ostringstream tmp_wkt;は、default precisionセットです。現在のところ、プログラムはすべての数字を書いていないので、丸めが適用されています。

tmp_wkt << boost::geometry::wkt(test_erosion);の前にtmp_wkt.precision(16);を追加すると、ブロックを持たないのと同じ動作になります。なぜなら、すべての数字が書き込まれるためです。ここで

はアクションでこれらの点を表示する更新プログラムです。

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

int main() 
{ 
    std::string wkt = "MULTIPOLYGON(((-203.3984972480392 326.87043766411114,-234.3294031269611 350.72117460025004,-234.32940582512484 350.7211767561067,-234.59541944833873 350.9413566745228,-234.5954246133754 350.9413612592119,-234.8456066177885 351.1793768235705,-234.84561145406377 351.179381753826,-235.078768547128 351.43409770182103,-235.07877303157431 351.43410295412707,-235.29379312442313 351.70430436766964,-235.29379723565108 351.7043099169743,-235.39951413618792 351.85781786966413,-240.86780715032046 350.38218215855835,-241.2049443604434 350.30361570297174,-241.20495115354115 350.3036143659985,-241.5467165739732 350.24856362767656,-241.54672344329876 350.24856276394,-241.89147886679623 350.21729162130026,-241.89148577942245 350.2172912349408,-242.23758558935015 350.20994967493,-242.58335698974216 350.2265727030494,-242.5833638895166 350.22657327470256,-242.9271563937872 350.26708130353956,-242.92716323747084 350.2670823512364,-243.26732892181855 350.3312812109238,-243.26733567660713 350.3312827296422,-243.60225063542637 350.4188666739157,-243.93029626301933 350.52941192532916,-243.93030274346452 350.52941436202866,-244.24991952642313 350.66239589829064,-244.55956286161836 350.81717054531686,-244.55956894361645 350.81717385333343,-244.8577608930744 350.99300259862656,-244.85776673160544 350.99300631954446,-245.14307795174008 351.18904635131906,-245.1430835188178 351.18905046730254,-245.41415167705114 351.40436658497003,-245.6696669314724 351.6379177381484,-245.66967187701746 351.63792258327567,-245.90841706208894 351.88859631483484,-266.58920031948566 375.16554041806563,-266.58920258870927 375.16554306360825,-266.8114462984894 375.433970996735,-266.8114505535744 375.43397651693255,-267.0144568842047 375.7172330288498,-267.0144607444406 375.7172388320306,-267.19724352509485 376.01394790994334,-267.1972469717292 376.0139539679166,-267.358918274207 376.32267424871253,-267.35892129049665 376.3226805320497,-267.49869574263016 376.6419123042001,-267.4986983139225 376.6419187823777,-267.6158969147833 376.97011127128593,-267.6158990285875 376.970117912834,-267.7099540930073 377.30568358689385,-267.7804054331035 377.6469788117333,-267.780406603398 377.6469856825949,-267.8269143132387 377.99236621139704,-267.8492510917757 378.34014040558645,-267.84925129584775 378.3401473724138,-267.84730904189666 378.68863970288874,-267.8210977526416 379.03614335774023,-267.8210969865306 379.036150285323,-267.7707424635338 379.3809909713855,-267.6964900867632 379.72148658265553,-267.59870274954784 380.0559764307823,-267.5987005618558 380.05598304835985,-267.4778489339802 380.38285544057135,-267.3345253662763 380.7005096185073,-267.334522280147 380.700515867838,-267.1694203712224 381.00741516970913,-267.1694168572867 381.0074211888939,-266.9833347199501 381.3020805089815,-266.77718414040345 381.58305694993714,-266.7771798240608 381.58306242236944,-266.5519583226944 381.8489968074004,-266.5519536356491 381.8490019658822,-266.30875282540296 382.09860488379184,-232.51589024775978 414.4450812583296,-232.51588002802416 414.4450898114167,-232.51586876173633 414.4450969296367,-232.51585664898366 414.445102486571,-232.51584390488657 414.4451063835295,-232.5158373664838 414.445107686701,-211.12681324719696 417.9713206571314,-211.12680695294904 417.97132149052527,-211.1267942693878 417.9713219522357,-211.12678793120457 417.971321578691,-211.1267816295017 417.9713208036793,-211.12676923690148 417.97131806335767,-211.1267572912145 417.97131377541353,-211.12675154646425 417.9713110717222,-177.1106691504801 400.6223337146699,-177.1106636027793 400.62233015463886,-177.11065830167098 400.6223262368518,-177.11064853019522 400.6223173975823,-177.11064000569968 400.62230735032404,-177.11063625823746 400.6223019274713,-177.11063287618194 400.6222962695118,-177.11062726542067 400.6222843475245,-177.11062327082684 400.622271791345,-177.11062190239758 400.6222653432285,-165.59426937600804 335.9234066092942,-162.6596781566315 302.06171116087233,-162.6596788436905 302.0616975137797,-162.65967988463825 302.06169075731424,-162.65968333706937 302.06167753627386,-162.65968573241835 302.0616711334854,-162.6596885596208 302.06166490931287,-162.65969545477958 302.06165311219564,-162.65970389380263 302.0616423651924,-162.65970864407186 302.06163744906183,-162.65971909523134 302.0616286463092,-162.65973064885196 302.0616213504858,-162.65974308921002 302.0616156978157,-162.6597561840252 302.0616117938428,-162.65976290080164 302.0616105217139,-162.65977651628992 302.06160936686865,-162.65979016210093 302.0616100789291,-162.65979691664793 302.06161113225346,-162.65981013134098 302.0616146089008,-162.65982274871268 302.0616198545771,-204.8758528204258 323.10306070098704,-204.8758584840069 323.10306427432,-204.87586903132672 323.1030725164298,-204.87587838335946 323.10308209337154,-204.87588255785658 323.1030873296329,-204.87588981029387 323.1030985804321,-204.8758928557106 323.103104544516,-204.87589549513 323.1031106990528,-204.87589771671574 323.10311701644275,-204.87590086845387 323.1031300258577,-204.87590225445257 323.1031433396602,-204.8759018498778 323.10315671929584,-204.8444560373964 323.42562807154223,-204.84445513319602 323.42563489982314,-204.78751382477697 323.76528940556193,-204.78751245267617 323.76529615540176,-204.70732324106254 324.10023186228716,-204.60427022620226 324.42884648764846,-204.60426794001853 324.4288529850604,-204.47883820282144 324.74959412196023,-204.47883547479194 324.74960044658303,-204.33162256579686 325.0609494910012,-203.3984972480392 326.87043766411114)))"; 

    typedef double coordinate_2d; 
    typedef boost::geometry::model::d2::point_xy<coordinate_2d> point_2d; 
    typedef boost::geometry::model::polygon<point_2d> polygon_2d; 
    typedef boost::geometry::model::multi_polygon<polygon_2d> multi_polygon_2d; 
    multi_polygon_2d test_erosion, tmp_erosion; 

    // Read WKT 
    boost::geometry::read_wkt(wkt, test_erosion); 

    // Check validity 
    std::cout << boost::geometry::is_valid(test_erosion) << std::endl; 

    ////////////////////////////////////////////// 
    // WHY DO I NEED THIS BLOCK??? 
    ////////////////////////////////////////////// 
    // Export to wkt 
    std::ostringstream tmp_wkt; 
    tmp_wkt.precision(16); // changing the precision to include all digits will render this block moot 
    tmp_wkt << boost::geometry::wkt(test_erosion); // this will round according to the precision for the stream 

    // And read it again 
    boost::geometry::read_wkt(tmp_wkt.str(), test_erosion); 
    std::cout << boost::geometry::is_valid(test_erosion) << std::endl; 
    ////////////////////////////////////////////// 

    // Apply buffer 
    boost::geometry::buffer(test_erosion, tmp_erosion, 
          boost::geometry::strategy::buffer::distance_symmetric<double>(-0.0000001), // this will produce output in tmp_erosion, even with all the digits 
          //boost::geometry::strategy::buffer::distance_symmetric<double>(-0.00001), // this will not produce output if the coordinates are not rounded 
          boost::geometry::strategy::buffer::side_straight(), 
          boost::geometry::strategy::buffer::join_round(), 
          boost::geometry::strategy::buffer::end_round(), 
          boost::geometry::strategy::buffer::point_circle(360) 
          ); 

    // Print result 
    std::cout << boost::geometry::wkt(test_erosion) << std::endl; 
    std::cout << boost::geometry::wkt(tmp_erosion) << std::endl;;