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 /* * 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 "include/core/SkPoint.h" #include "include/core/SkScalar.h" #include struct SkRect; template class SkTDArray; /** * Generates a polygon that is inset a constant from the boundary of a given convex polygon. * The input polygon is expected to have values clamped to the nearest 1/16th. * * @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. */ bool SkInsetConvexPolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, SkScalar inset, SkTDArray* insetPolygon); /** * 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, have no coincident vertices or collinear edges, and have * values clamped to the nearest 1/16th. * * @param inputPolygonVerts Array of points representing the vertices of the original polygon. * @param inputPolygonSize Number of vertices in the original polygon. * @param bounds Bounding rectangle for 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. */ bool SkOffsetSimplePolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize, const SkRect& bounds, SkScalar offset, SkTDArray* offsetPolygon, SkTDArray* polygonIndices = nullptr); /** * 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 |offset| -- 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 offset Offset value (can be negative). * @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. * @return true for success, false otherwise */ bool SkComputeRadialSteps(const SkVector& offset0, const SkVector& offset1, SkScalar offset, 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. * The polygon is also expected to have values clamped to the nearest 1/16th. * * @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* triangleIndices); // Experiment: doesn't handle really big floats (returns false), always returns true for count <= 3 bool SkIsPolyConvex_experimental(const SkPoint[], int count); #endif