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Diffstat (limited to 'src/utils/SkPolyUtils.h')
| -rwxr-xr-x | src/utils/SkPolyUtils.h | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/src/utils/SkPolyUtils.h b/src/utils/SkPolyUtils.h new file mode 100755 index 0000000000..ab5ebb8d40 --- /dev/null +++ b/src/utils/SkPolyUtils.h @@ -0,0 +1,143 @@ +/* + * 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 whether a polygon is simple (i.e., not self-intersecting) 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 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 |