1 /************************************************************** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, 14 * software distributed under the License is distributed on an 15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 16 * KIND, either express or implied. See the License for the 17 * specific language governing permissions and limitations 18 * under the License. 19 * 20 *************************************************************/ 21 22 23 24 #ifndef _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX 25 #define _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX 26 27 #include <basegfx/polygon/b2dpolypolygon.hxx> 28 #include <basegfx/basegfxdllapi.h> 29 30 ////////////////////////////////////////////////////////////////////////////// 31 32 namespace basegfx 33 { 34 namespace tools 35 { 36 // Solve all crossovers in a polyPolygon. This re-layouts all contained polygons so that the 37 // result will contain only non-cutting polygons. For that reason, points will be added at 38 // crossover and touch points and the single Polygons may be re-combined. The orientations 39 // of the contained polygons in not changed but used as topological information. 40 // Self crossovers of the contained sub-polygons are implicitly handled, but to not lose 41 // the topological information, it may be necessary to remove self-intersections of the 42 // contained sub-polygons in a preparing step and to explicitly correct their orientations. 43 BASEGFX_DLLPUBLIC B2DPolyPolygon solveCrossovers(const B2DPolyPolygon& rCandidate); 44 45 // Version for single polygons. This is for solving self-intersections. Result will be free of 46 // crossovers. When result contains multiple polygons, it may be necessary to rearrange their 47 // orientations since holes may have been created (use correctOrientations eventually). 48 BASEGFX_DLLPUBLIC B2DPolyPolygon solveCrossovers(const B2DPolygon& rCandidate); 49 50 // Neutral polygons will be stripped. Neutral polygons are ones who's orientation is 51 // neutral, so normally they have no volume -> just closed paths. A polygon with the same 52 // positive and negative oriented volume is also neutral, so this may not be wanted. It is 53 // safe to call with crossover-free polygons, though (that's where it's mostly used). 54 BASEGFX_DLLPUBLIC B2DPolyPolygon stripNeutralPolygons(const B2DPolyPolygon& rCandidate); 55 56 // Remove not necessary polygons. Works only correct with crossover-free polygons. For each 57 // polygon, the depth for the PolyPolygon is calculated. The orientation is used to identify holes. 58 // Start value for holes is -1, for polygons it's zero. Ech time a polygon is contained in another one, 59 // it's depth is increased when inside a polygon, decreased when inside a hole. The result is a depth 60 // which e.g. is -1 for holes outside everything, 1 for a polygon covered by another polygon and zero 61 // for e.g. holes in a polygon or polygons outside everythig else. 62 // In the 2nd step, all polygons with depth other than zero are removed. If bKeepAboveZero is used, 63 // all polygons < 1 are removed. The bKeepAboveZero mode is useful for clipping, e.g. just append 64 // one polygon to another and use this mode -> only parts where two polygons overlapped will be kept. 65 // In combination with correct orientation of the input orientations and the SolveCrossover calls this 66 // can be combined for logical polygon operations or polygon clipping. 67 BASEGFX_DLLPUBLIC B2DPolyPolygon stripDispensablePolygons(const B2DPolyPolygon& rCandidate, bool bKeepAboveZero = false); 68 69 // geometrically convert PolyPolygons which are proposed to use nonzero fill rule 70 // to a representation where evenodd paint will give the same result. To do this 71 // all intersections and self-intersections get solved (the polygons will be rearranged 72 // if needed). Then all polygons which are inside another one with the same orientation 73 // get deleted 74 BASEGFX_DLLPUBLIC B2DPolyPolygon createNonzeroConform(const B2DPolyPolygon& rCandidate); 75 76 // For convenience: The four basic operations OR, XOR, AND and DIFF for 77 // two PolyPolygons. These are combinations of the above methods. To not be forced 78 // to do evtl. already done preparations twice, You have to do the operations Yourself. 79 // 80 // A source preparation consists of preparing it to be seen as XOR-Rule PolyPolygon, 81 // so it is freed of intersections, self-intersections and the orientations are corrected. 82 // Important is that it will define the same areas as before, but is intersection-free. 83 // As an example think about a single polygon looping in itself and having holes. To 84 // topologically correctly handle this, it is necessary to remove all intersections and 85 // to correct the orientations. The orientation of the isolated holes e.g. will be negative. 86 // Topologically it is necessary to prepare each polygon which is seen as entity. It is 87 // not sufficient just to concatenate them and prepare the result, this may be topologically 88 // different since the simple concatenation will be seen as XOR. To work correctly, You 89 // may need to OR those polygons. 90 91 // Preparations: solve self-intersections and intersections, remove neutral 92 // parts and correct orientations. 93 BASEGFX_DLLPUBLIC B2DPolyPolygon prepareForPolygonOperation(const B2DPolygon& rCandidate); 94 BASEGFX_DLLPUBLIC B2DPolyPolygon prepareForPolygonOperation(const B2DPolyPolygon& rCandidate); 95 96 // OR: Return all areas where CandidateA or CandidateB exist 97 BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationOr(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 98 99 // XOR: Return all areas where CandidateA or CandidateB exist, but not both 100 BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationXor(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 101 102 // AND: Return all areas where CandidateA and CandidateB exist 103 BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationAnd(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 104 105 // DIFF: Return all areas where CandidateA is not covered by CandidateB (cut B out of A) 106 BASEGFX_DLLPUBLIC B2DPolyPolygon solvePolygonOperationDiff(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 107 108 /** merge all single PolyPolygons to a single, OR-ed PolyPolygon 109 110 @param rInput 111 The source PolyPolygons 112 113 @return A single PolyPolygon containing the Or-merged result 114 */ 115 BASEGFX_DLLPUBLIC B2DPolyPolygon mergeToSinglePolyPolygon(const B2DPolyPolygonVector& rInput); 116 117 } // end of namespace tools 118 } // end of namespace basegfx 119 120 ////////////////////////////////////////////////////////////////////////////// 121 122 123 #endif /* _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX */ 124