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 29 ////////////////////////////////////////////////////////////////////////////// 30 31 namespace basegfx 32 { 33 namespace tools 34 { 35 // Solve all crossovers in a polyPolygon. This re-layouts all contained polygons so that the 36 // result will contain only non-cutting polygons. For that reason, points will be added at 37 // crossover and touch points and the single Polygons may be re-combined. The orientations 38 // of the contained polygons in not changed but used as topological information. 39 // Self crossovers of the contained sub-polygons are implicitely handled, but to not lose 40 // the topological information, it may be necessary to remove self-intersections of the 41 // contained sub-polygons in a preparing step and to explicitely correct their orientations. 42 B2DPolyPolygon solveCrossovers(const B2DPolyPolygon& rCandidate); 43 44 // Version for single polygons. This is for solving self-intersections. Result will be free of 45 // crossovers. When result contains multiple polygons, it may be necessary to rearrange their 46 // orientations since holes may have been created (use correctOrientations eventually). 47 B2DPolyPolygon solveCrossovers(const B2DPolygon& rCandidate); 48 49 // Neutral polygons will be stripped. Neutral polygons are ones who's orientation is 50 // neutral, so normally they have no volume -> just closed paths. A polygon with the same 51 // positive and negative oriented volume is also neutral, so this may not be wanted. It is 52 // safe to call with crossover-free polygons, though (that's where it's mostly used). 53 B2DPolyPolygon stripNeutralPolygons(const B2DPolyPolygon& rCandidate); 54 55 // Remove not necessary polygons. Works only correct with crossover-free polygons. For each 56 // polygon, the depth for the PolyPolygon is calculated. The orientation is used to identify holes. 57 // Start value for holes is -1, for polygons it's zero. Ech time a polygon is contained in another one, 58 // it's depth is increased when inside a polygon, decreased when inside a hole. The result is a depth 59 // which e.g. is -1 for holes outside everything, 1 for a polygon covered by another polygon and zero 60 // for e.g. holes in a polygon or polygons outside everythig else. 61 // In the 2nd step, all polygons with depth other than zero are removed. If bKeepAboveZero is used, 62 // all polygons < 1 are removed. The bKeepAboveZero mode is useful for clipping, e.g. just append 63 // one polygon to another and use this mode -> only parts where two polygons overlapped will be kept. 64 // In combination with correct orientation of the input orientations and the SolveCrossover calls this 65 // can be combined for logical polygon operations or polygon clipping. 66 B2DPolyPolygon stripDispensablePolygons(const B2DPolyPolygon& rCandidate, bool bKeepAboveZero = false); 67 68 // geometrically convert PolyPolygons which are proposed to use nonzero fill rule 69 // to a representation where evenodd paint will give the same result. To do this 70 // all intersections and self-intersections get solved (the polygons will be rearranged 71 // if needed). Then all polygons which are inside another one with the same orientation 72 // get deleted 73 B2DPolyPolygon createNonzeroConform(const B2DPolyPolygon& rCandidate); 74 75 // For convenience: The four basic operations OR, XOR, AND and DIFF for 76 // two PolyPolygons. These are combinations of the above methods. To not be forced 77 // to do evtl. already done preparations twice, You have to do the operations Yourself. 78 // 79 // A source preparation consists of preparing it to be seen as XOR-Rule PolyPolygon, 80 // so it is freed of intersections, self-intersections and the orientations are corrected. 81 // Important is that it will define the same areas as before, but is intersection-free. 82 // As an example think about a single polygon looping in itself and having holes. To 83 // topologically correctly handle this, it is necessary to remove all intersections and 84 // to correct the orientations. The orientation of the isolated holes e.g. will be negative. 85 // Topologically it is necessary to prepare each polygon which is seen as entity. It is 86 // not sufficient just to concatenate them and prepare the result, this may be topologically 87 // different since the simple concatenation will be seen as XOR. To work correctly, You 88 // may need to OR those polygons. 89 90 // Preparations: solve self-intersections and intersections, remove neutral 91 // parts and correct orientations. 92 B2DPolyPolygon prepareForPolygonOperation(const B2DPolygon& rCandidate); 93 B2DPolyPolygon prepareForPolygonOperation(const B2DPolyPolygon& rCandidate); 94 95 // OR: Return all areas where CandidateA or CandidateB exist 96 B2DPolyPolygon solvePolygonOperationOr(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 97 98 // XOR: Return all areas where CandidateA or CandidateB exist, but not both 99 B2DPolyPolygon solvePolygonOperationXor(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 100 101 // AND: Return all areas where CandidateA and CandidateB exist 102 B2DPolyPolygon solvePolygonOperationAnd(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 103 104 // DIFF: Return all areas where CandidateA is not covered by CandidateB (cut B out of A) 105 B2DPolyPolygon solvePolygonOperationDiff(const B2DPolyPolygon& rCandidateA, const B2DPolyPolygon& rCandidateB); 106 107 /** merge all single PolyPolygons to a single, OR-ed PolyPolygon 108 109 @param rInput 110 The source PolyPolygons 111 112 @return A single PolyPolygon containing the Or-merged result 113 */ 114 B2DPolyPolygon mergeToSinglePolyPolygon(const B2DPolyPolygonVector& rInput); 115 116 } // end of namespace tools 117 } // end of namespace basegfx 118 119 ////////////////////////////////////////////////////////////////////////////// 120 121 122 #endif /* _BGFX_POLYGON_B2DPOLYPOLYGONCUTTER_HXX */ 123