| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkOffsetPolygon_DEFINED |
| #define SkOffsetPolygon_DEFINED |
| |
| #include <functional> |
| |
| #include "SkTDArray.h" |
| #include "SkPoint.h" |
| |
| /** |
| * Generates a polygon that is inset a variable distance (controlled by offsetDistanceFunc) |
| * from the boundary of a given convex polygon. |
| * |
| * @param inputPolygonVerts Array of points representing the vertices of the original polygon. |
| * It should be convex and have no coincident points. |
| * @param inputPolygonSize Number of vertices in the original polygon. |
| * @param insetDistanceFunc How far we wish to inset the polygon for a given position. |
| * This should return a positive value. |
| * @param insetPolygon The resulting inset polygon, if any. |
| * @return true if an inset polygon exists, false otherwise. |
| */ |
| bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, |
| std::function<SkScalar(const SkPoint&)> insetDistanceFunc, |
| SkTDArray<SkPoint>* insetPolygon); |
| |
| /** |
| * Generates a polygon that is inset a constant from the boundary of a given convex polygon. |
| * |
| * @param inputPolygonVerts Array of points representing the vertices of the original polygon. |
| * It should be convex and have no coincident points. |
| * @param inputPolygonSize Number of vertices in the original polygon. |
| * @param inset How far we wish to inset the polygon. This should be a positive value. |
| * @param insetPolygon The resulting inset polygon, if any. |
| * @return true if an inset polygon exists, false otherwise. |
| */ |
| inline bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, |
| SkScalar inset, SkTDArray<SkPoint>* insetPolygon) { |
| return SkInsetConvexPolygon(inputPolygonVerts, inputPolygonSize, |
| [inset](const SkPoint&) { return inset; }, |
| insetPolygon); |
| } |
| |
| /** |
| * Generates a simple polygon (if possible) that is offset a variable distance (controlled by |
| * offsetDistanceFunc) from the boundary of a given simple polygon. |
| * The input polygon must be simple and have no coincident vertices or collinear edges. |
| * |
| * @param inputPolygonVerts Array of points representing the vertices of the original polygon. |
| * @param inputPolygonSize Number of vertices in the original polygon. |
| * @param offsetDistanceFunc How far we wish to offset the polygon for a given position. |
| * Positive values indicate insetting, negative values outsetting. |
| * @param offsetPolgon The resulting offset polygon, if any. |
| * @param polygonIndices The indices of the original polygon that map to the new one. |
| * @return true if an offset simple polygon exists, false otherwise. |
| */ |
| bool SkOffsetSimplePolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, |
| std::function<SkScalar(const SkPoint&)> offsetDistanceFunc, |
| SkTDArray<SkPoint>* offsetPolygon, |
| SkTDArray<int>* polygonIndices = nullptr); |
| |
| /** |
| * Generates a simple polygon (if possible) that is offset a constant distance from the boundary |
| * of a given simple polygon. |
| * The input polygon must be simple and have no coincident vertices or collinear edges. |
| * |
| * @param inputPolygonVerts Array of points representing the vertices of the original polygon. |
| * @param inputPolygonSize Number of vertices in the original polygon. |
| * @param offset How far we wish to offset the polygon. |
| * Positive values indicate insetting, negative values outsetting. |
| * @param offsetPolgon The resulting offset polygon, if any. |
| * @param polygonIndices The indices of the original polygon that map to the new one. |
| * @return true if an offset simple polygon exists, false otherwise. |
| */ |
| inline bool SkOffsetSimplePolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, |
| SkScalar offset, SkTDArray<SkPoint>* offsetPolygon, |
| SkTDArray<int>* polygonIndices = nullptr) { |
| return SkOffsetSimplePolygon(inputPolygonVerts, inputPolygonSize, |
| [offset](const SkPoint&) { return offset; }, |
| offsetPolygon, polygonIndices); |
| } |
| |
| /** |
| * Offset a segment by the given distance at each point. |
| * Uses the outer tangents of two circles centered on each endpoint. |
| * See: https://en.wikipedia.org/wiki/Tangent_lines_to_circles |
| * |
| * @param p0 First endpoint. |
| * @param p1 Second endpoint. |
| * @param d0 Offset distance from first endpoint. |
| * @param d1 Offset distance from second endpoint. |
| * @param side Indicates whether we want to offset to the left (1) or right (-1) side of segment. |
| * @param offset0 First endpoint of offset segment. |
| * @param offset1 Second endpoint of offset segment. |
| * @return true if an offset segment exists, false otherwise. |
| */ |
| bool SkOffsetSegment(const SkPoint& p0, const SkPoint& p1, SkScalar d0, SkScalar d1, |
| int side, SkPoint* offset0, SkPoint* offset1); |
| |
| /** |
| * Compute the number of points needed for a circular join when offsetting a vertex. |
| * The lengths of offset0 and offset1 don't have to equal r -- only the direction matters. |
| * The segment lengths will be approximately four pixels. |
| * |
| * @param offset0 Starting offset vector direction. |
| * @param offset1 Ending offset vector direction. |
| * @param r Length of offset. |
| * @param rotSin Sine of rotation delta per step. |
| * @param rotCos Cosine of rotation delta per step. |
| * @param n Number of steps to fill out the arc. |
| */ |
| void SkComputeRadialSteps(const SkVector& offset0, const SkVector& offset1, SkScalar r, |
| SkScalar* rotSin, SkScalar* rotCos, int* n); |
| |
| /** |
| * Determine winding direction for a polygon. |
| * The input polygon must be simple or the result will be meaningless. |
| * |
| * @param polygonVerts Array of points representing the vertices of the polygon. |
| * @param polygonSize Number of vertices in the polygon. |
| * @return 1 for cw, -1 for ccw, and 0 if zero signed area (either degenerate or self-intersecting). |
| * The y-axis is assumed to be pointing down. |
| */ |
| int SkGetPolygonWinding(const SkPoint* polygonVerts, int polygonSize); |
| |
| /** |
| * Determine whether a polygon is convex or not. |
| * |
| * @param polygonVerts Array of points representing the vertices of the polygon. |
| * @param polygonSize Number of vertices in the polygon. |
| * @return true if the polygon is convex, false otherwise. |
| */ |
| bool SkIsConvexPolygon(const SkPoint* polygonVerts, int polygonSize); |
| |
| /** |
| * Determine whether a polygon is simple (i.e., not self-intersecting) or not. |
| * The input polygon must have no coincident vertices or the test will fail. |
| * |
| * @param polygonVerts Array of points representing the vertices of the polygon. |
| * @param polygonSize Number of vertices in the polygon. |
| * @return true if the polygon is simple, false otherwise. |
| */ |
| bool SkIsSimplePolygon(const SkPoint* polygonVerts, int polygonSize); |
| |
| /** |
| * Compute indices to triangulate the given polygon. |
| * The input polygon must be simple (i.e. it is not self-intersecting) |
| * and have no coincident vertices or collinear edges. |
| * |
| * @param polygonVerts Array of points representing the vertices of the polygon. |
| * @param indexMap Mapping from index in the given array to the final index in the triangulation. |
| * @param polygonSize Number of vertices in the polygon. |
| * @param triangleIndices Indices of the resulting triangulation. |
| * @return true if successful, false otherwise. |
| */ |
| bool SkTriangulateSimplePolygon(const SkPoint* polygonVerts, uint16_t* indexMap, int polygonSize, |
| SkTDArray<uint16_t>* triangleIndices); |
| |
| #endif |