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See the License for the * specific language governing permissions and limitations * under the License. * *************************************************************/ #ifndef _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX #define _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX #include #include ////////////////////////////////////////////////////////////////////////////// namespace basegfx { namespace tools { // Solve all crossovers in a polyPolygon. This re-layouts all contained polygons so that the // result will contain only non-cutting polygons. For that reason, points will be added at // crossover and touch points and the single Polygons may be re-combined. The orientations // of the contained polygons in not changed but used as topological information. // Self crossovers of the contained sub-polygons are implicitly handled, but to not lose // the topological information, it may be necessary to remove self-intersections of the // contained sub-polygons in a preparing step and to explicitly correct their orientations. BASEGFX_DLLPUBLIC B2DPolyPolygon solveCrossovers(const B2DPolyPolygon& rCandidate); // Version for single polygons. This is for solving self-intersections. Result will be free of // crossovers. When result contains multiple polygons, it may be necessary to rearrange their // orientations since holes may have been created (use correctOrientations eventually). BASEGFX_DLLPUBLIC B2DPolyPolygon solveCrossovers(const B2DPolygon& rCandidate); // Neutral polygons will be stripped. Neutral polygons are ones who's orientation is // neutral, so normally they have no volume -> just closed paths. A polygon with the same // positive and negative oriented volume is also neutral, so this may not be wanted. It is // safe to call with crossover-free polygons, though (that's where it's mostly used). BASEGFX_DLLPUBLIC B2DPolyPolygon stripNeutralPolygons(const B2DPolyPolygon& rCandidate); // Remove not necessary polygons. Works only correct with crossover-free polygons. For each // polygon, the depth for the PolyPolygon is calculated. The orientation is used to identify holes. // Start value for holes is -1, for polygons it's zero. Ech time a polygon is contained in another one, // it's depth is increased when inside a polygon, decreased when inside a hole. The result is a depth // which e.g. is -1 for holes outside everything, 1 for a polygon covered by another polygon and zero // for e.g. holes in a polygon or polygons outside everythig else. // In the 2nd step, all polygons with depth other than zero are removed. If bKeepAboveZero is used, // all polygons < 1 are removed. The bKeepAboveZero mode is useful for clipping, e.g. just append // one polygon to another and use this mode -> only parts where two polygons overlapped will be kept. // In combination with correct orientation of the input orientations and the SolveCrossover calls this // can be combined for logical polygon operations or polygon clipping. BASEGFX_DLLPUBLIC B2DPolyPolygon stripDispensablePolygons(const B2DPolyPolygon& rCandidate, bool bKeepAboveZero = false); // geometrically convert PolyPolygons which are proposed to use nonzero fill rule // to a representation where evenodd paint will give the same result. To do this // all intersections and self-intersections get solved (the polygons will be rearranged // if needed). Then all polygons which are inside another one with the same orientation // get deleted BASEGFX_DLLPUBLIC B2DPolyPolygon createNonzeroConform(const B2DPolyPolygon& rCandidate); // For convenience: The four basic operations OR, XOR, AND and DIFF for // two PolyPolygons. These are combinations of the above methods. To not be forced // to do evtl. already done preparations twice, You have to do the operations Yourself. // // A source preparation consists of preparing it to be seen as XOR-Rule PolyPolygon, // so it is freed of intersections, self-intersections and the orientations are corrected. // Important is that it will define the same areas as before, but is intersection-free. // As an example think about a single polygon looping in itself and having holes. To // topologically correctly handle this, it is necessary to remove all intersections and // to correct the orientations. The orientation of the isolated holes e.g. will be negative. // Topologically it is necessary to prepare each polygon which is seen as entity. It is // not sufficient just to concatenate them and prepare the result, this may be topologically // different since the simple concatenation will be seen as XOR. To work correctly, You // may need to OR those polygons. // Preparations: solve self-intersections and intersections, remove neutral // parts and correct orientations. BASEGFX_DLLPUBLIC B2DPolyPolygon prepareForPolygonOperation(const B2DPolygon& rCandidate); BASEGFX_DLLPUBLIC B2DPolyPolygon prepareForPolygonOperation(const B2DPolyPolygon& rCandidate); // OR: Return all areas where CandidateA or CandidateB exist BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationOr(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); // XOR: Return all areas where CandidateA or CandidateB exist, but not both BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationXor(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); // AND: Return all areas where CandidateA and CandidateB exist BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationAnd(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); // DIFF: Return all areas where CandidateA is not covered by CandidateB (cut B out of A) BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationDiff(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); /** merge all single PolyPolygons to a single, OR-ed PolyPolygon @param rInput The source PolyPolygons @return A single PolyPolygon containing the Or-merged result */ BASEGFX_DLLPUBLIC B2DPolyPolygon mergeToSinglePolyPolygon(const B2DPolyPolygonVector& rInput); } // end of namespace tools } // end of namespace basegfx ////////////////////////////////////////////////////////////////////////////// #endif /* _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX */