1 /* 2 * Copyright 2017 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkInsetConvexPolygon_DEFINED 9 #define SkInsetConvexPolygon_DEFINED 10 11 #include <functional> 12 13 #include "SkTDArray.h" 14 #include "SkPoint.h" 15 16 /** 17 * Generates a polygon that is inset a given distance from the boundary of a given convex polygon. 18 * 19 * @param inputPolygonVerts Array of points representing the vertices of the original polygon. 20 * It should be convex and have no coincident points. 21 * @param inputPolygonSize Number of vertices in the original polygon. 22 * @param insetDistanceFunc How far we wish to inset the polygon for a given index in the array. 23 * This should return a positive value. 24 * @param insetPolygon The resulting inset polygon, if any. 25 * @return true if an inset polygon exists, false otherwise. 26 */ 27 bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, 28 std::function<SkScalar(int index)> insetDistanceFunc, 29 SkTDArray<SkPoint>* insetPolygon); 30 31 inline bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, 32 SkScalar inset, 33 SkTDArray<SkPoint>* insetPolygon) { 34 return SkInsetConvexPolygon(inputPolygonVerts, inputPolygonSize, 35 [inset](int) { return inset; }, 36 insetPolygon); 37 } 38 39 /** 40 * Offset a segment by the given distance at each point. 41 * Uses the outer tangents of two circles centered on each endpoint. 42 * See: https://en.wikipedia.org/wiki/Tangent_lines_to_circles 43 * 44 * @param p0 First endpoint. 45 * @param p1 Second endpoint. 46 * @param d0 Offset distance from first endpoint. 47 * @param d1 Offset distance from second endpoint. 48 * @param side Indicates whether we want to offset to the left (1) or right (-1) side of segment. 49 * @param offset0 First endpoint of offset segment. 50 * @param offset1 Second endpoint of offset segment. 51 * @return true if an offset segment exists, false otherwise. 52 */ 53 bool SkOffsetSegment(const SkPoint& p0, const SkPoint& p1, SkScalar d0, SkScalar d1, 54 int side, SkPoint* offset0, SkPoint* offset1); 55 56 #endif 57
