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Diffstat (limited to 'gfx/skia/skia/src/pathops/SkLineParameters.h')
| -rw-r--r-- | gfx/skia/skia/src/pathops/SkLineParameters.h | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/pathops/SkLineParameters.h b/gfx/skia/skia/src/pathops/SkLineParameters.h new file mode 100644 index 0000000000..45d1ed4ed6 --- /dev/null +++ b/gfx/skia/skia/src/pathops/SkLineParameters.h @@ -0,0 +1,181 @@ +/* + * Copyright 2012 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef SkLineParameters_DEFINED +#define SkLineParameters_DEFINED + +#include "src/pathops/SkPathOpsCubic.h" +#include "src/pathops/SkPathOpsLine.h" +#include "src/pathops/SkPathOpsQuad.h" + +// Sources +// computer-aided design - volume 22 number 9 november 1990 pp 538 - 549 +// online at http://cagd.cs.byu.edu/~tom/papers/bezclip.pdf + +// This turns a line segment into a parameterized line, of the form +// ax + by + c = 0 +// When a^2 + b^2 == 1, the line is normalized. +// The distance to the line for (x, y) is d(x,y) = ax + by + c +// +// Note that the distances below are not necessarily normalized. To get the true +// distance, it's necessary to either call normalize() after xxxEndPoints(), or +// divide the result of xxxDistance() by sqrt(normalSquared()) + +class SkLineParameters { +public: + + bool cubicEndPoints(const SkDCubic& pts) { + int endIndex = 1; + cubicEndPoints(pts, 0, endIndex); + if (dy() != 0) { + return true; + } + if (dx() == 0) { + cubicEndPoints(pts, 0, ++endIndex); + SkASSERT(endIndex == 2); + if (dy() != 0) { + return true; + } + if (dx() == 0) { + cubicEndPoints(pts, 0, ++endIndex); // line + SkASSERT(endIndex == 3); + return false; + } + } + // FIXME: after switching to round sort, remove bumping fA + if (dx() < 0) { // only worry about y bias when breaking cw/ccw tie + return true; + } + // if cubic tangent is on x axis, look at next control point to break tie + // control point may be approximate, so it must move significantly to account for error + if (NotAlmostEqualUlps(pts[0].fY, pts[++endIndex].fY)) { + if (pts[0].fY > pts[endIndex].fY) { + fA = DBL_EPSILON; // push it from 0 to slightly negative (y() returns -a) + } + return true; + } + if (endIndex == 3) { + return true; + } + SkASSERT(endIndex == 2); + if (pts[0].fY > pts[3].fY) { + fA = DBL_EPSILON; // push it from 0 to slightly negative (y() returns -a) + } + return true; + } + + void cubicEndPoints(const SkDCubic& pts, int s, int e) { + fA = pts[s].fY - pts[e].fY; + fB = pts[e].fX - pts[s].fX; + fC = pts[s].fX * pts[e].fY - pts[e].fX * pts[s].fY; + } + + double cubicPart(const SkDCubic& part) { + cubicEndPoints(part); + if (part[0] == part[1] || ((const SkDLine& ) part[0]).nearRay(part[2])) { + return pointDistance(part[3]); + } + return pointDistance(part[2]); + } + + void lineEndPoints(const SkDLine& pts) { + fA = pts[0].fY - pts[1].fY; + fB = pts[1].fX - pts[0].fX; + fC = pts[0].fX * pts[1].fY - pts[1].fX * pts[0].fY; + } + + bool quadEndPoints(const SkDQuad& pts) { + quadEndPoints(pts, 0, 1); + if (dy() != 0) { + return true; + } + if (dx() == 0) { + quadEndPoints(pts, 0, 2); + return false; + } + if (dx() < 0) { // only worry about y bias when breaking cw/ccw tie + return true; + } + // FIXME: after switching to round sort, remove this + if (pts[0].fY > pts[2].fY) { + fA = DBL_EPSILON; + } + return true; + } + + void quadEndPoints(const SkDQuad& pts, int s, int e) { + fA = pts[s].fY - pts[e].fY; + fB = pts[e].fX - pts[s].fX; + fC = pts[s].fX * pts[e].fY - pts[e].fX * pts[s].fY; + } + + double quadPart(const SkDQuad& part) { + quadEndPoints(part); + return pointDistance(part[2]); + } + + double normalSquared() const { + return fA * fA + fB * fB; + } + + bool normalize() { + double normal = sqrt(normalSquared()); + if (approximately_zero(normal)) { + fA = fB = fC = 0; + return false; + } + double reciprocal = 1 / normal; + fA *= reciprocal; + fB *= reciprocal; + fC *= reciprocal; + return true; + } + + void cubicDistanceY(const SkDCubic& pts, SkDCubic& distance) const { + double oneThird = 1 / 3.0; + for (int index = 0; index < 4; ++index) { + distance[index].fX = index * oneThird; + distance[index].fY = fA * pts[index].fX + fB * pts[index].fY + fC; + } + } + + void quadDistanceY(const SkDQuad& pts, SkDQuad& distance) const { + double oneHalf = 1 / 2.0; + for (int index = 0; index < 3; ++index) { + distance[index].fX = index * oneHalf; + distance[index].fY = fA * pts[index].fX + fB * pts[index].fY + fC; + } + } + + double controlPtDistance(const SkDCubic& pts, int index) const { + SkASSERT(index == 1 || index == 2); + return fA * pts[index].fX + fB * pts[index].fY + fC; + } + + double controlPtDistance(const SkDQuad& pts) const { + return fA * pts[1].fX + fB * pts[1].fY + fC; + } + + double pointDistance(const SkDPoint& pt) const { + return fA * pt.fX + fB * pt.fY + fC; + } + + double dx() const { + return fB; + } + + double dy() const { + return -fA; + } + +private: + double fA; + double fB; + double fC; +}; + +#endif |