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/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkCurveMeasure_DEFINED
#define SkCurveMeasure_DEFINED
#include "SkPathMeasurePriv.h"
#include "SkPoint.h"
#include "SkNx.h"
// These are weights and abscissae for gaussian quadrature with weight function
// w(x) = 1
static SkScalar weights8[8] = {0.3626837833783620f, 0.3626837833783620f,
0.3137066458778873f, 0.3137066458778873f,
0.2223810344533745f, 0.2223810344533745f,
0.1012285362903763f, 0.1012285362903763f};
static SkScalar absc8[8] = {-0.1834346424956498f, 0.1834346424956498f,
-0.5255324099163290f, 0.5255324099163290f,
-0.7966664774136267f, 0.7966664774136267f,
-0.9602898564975363f, 0.9602898564975363f};
static Sk8f weights = Sk8f::Load(weights8);
static Sk8f absc = 0.5f*(Sk8f::Load(absc8) + 1.0f);
class ArcLengthIntegrator {
public:
ArcLengthIntegrator() {}
ArcLengthIntegrator(const SkPoint* pts, SkSegType segType);
SkScalar computeLength(SkScalar t);
private:
SkSegType fSegType;
// precomputed coefficients for derivatives in Horner form
Sk8f xCoeff[3];
Sk8f yCoeff[3];
};
class SkCurveMeasure {
public:
SkCurveMeasure() {}
// Almost exactly the same as in SkPath::Iter:
// kLine_SegType -> 2 points: start end
// kQuad_SegType -> 3 points: start control end
// kCubic_SegType -> 4 points: start control1 control2 end
// kConic_SegType -> 4 points: start control end (w, w)
//
// i.e. the only difference is that the conic's last point is a point
// consisting of the w value twice
SkCurveMeasure(const SkPoint* pts, SkSegType segType);
SkScalar getTime(SkScalar targetLength);
void getPosTanTime(SkScalar distance, SkPoint* pos, SkVector* tan, SkScalar* time);
SkScalar getLength();
private:
const SkScalar kTolerance = 0.0001f;
const int kNewtonIters = 5;
const int kBisectIters = 5;
SkSegType fSegType;
SkPoint fPts[4];
SkScalar fLength = -1.0f;
ArcLengthIntegrator fIntegrator;
// for debug purposes
int fIters;
};
#endif // SkCurveMeasure_DEFINED
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