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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 <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
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