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Refactor SkCurveMeasure to use existing eval code

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- Use quad, cubic, conic eval code from SkGeometry.h
- Implement evaluateDerivativeLength, evaluateDerivative and evaluate switch cases for lines along with the refactor

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2226973004

Review-Url: https://codereview.chromium.org/2226973004
This commit is contained in:
hstern 2016-08-10 10:55:09 -07:00 committed by Commit bot
parent cb0f4c3404
commit 4ab47e087e
2 changed files with 92 additions and 60 deletions
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136
src/utils/SkCurveMeasure.cpp
View File

@ -6,10 +6,66 @@
*/
#include "SkCurveMeasure.h"
#include "SkGeometry.h"
// for abs
#include <cmath>
#define UNIMPLEMENTED SkDEBUGF(("%s:%d unimplemented\n", __FILE__, __LINE__))
/// Used inside SkCurveMeasure::getTime's Newton's iteration
static inline SkPoint evaluate(const SkPoint pts[4], SkSegType segType,
SkScalar t) {
SkPoint pos;
switch (segType) {
case kQuad_SegType:
pos = SkEvalQuadAt(pts, t);
break;
case kLine_SegType:
pos = SkPoint::Make(SkScalarInterp(pts[0].x(), pts[1].x(), t),
SkScalarInterp(pts[0].y(), pts[1].y(), t));
break;
case kCubic_SegType:
SkEvalCubicAt(pts, t, &pos, nullptr, nullptr);
break;
case kConic_SegType: {
SkConic conic(pts, pts[3].x());
conic.evalAt(t, &pos);
}
break;
default:
UNIMPLEMENTED;
}
return pos;
}
/// Used inside SkCurveMeasure::getTime's Newton's iteration
static inline SkVector evaluateDerivative(const SkPoint pts[4],
SkSegType segType, SkScalar t) {
SkVector tan;
switch (segType) {
case kQuad_SegType:
tan = SkEvalQuadTangentAt(pts, t);
break;
case kLine_SegType:
tan = pts[1] - pts[0];
break;
case kCubic_SegType:
SkEvalCubicAt(pts, t, nullptr, &tan, nullptr);
break;
case kConic_SegType: {
SkConic conic(pts, pts[3].x());
conic.evalAt(t, nullptr, &tan);
}
break;
default:
UNIMPLEMENTED;
}
return tan;
}
/// Used in ArcLengthIntegrator::computeLength
static inline Sk8f evaluateDerivativeLength(const Sk8f& ts,
const Sk8f (&xCoeff)[3],
const Sk8f (&yCoeff)[3],
@ -22,17 +78,18 @@ static inline Sk8f evaluateDerivativeLength(const Sk8f& ts,
y = yCoeff[0]*ts + yCoeff[1];
break;
case kLine_SegType:
SkDebugf("Unimplemented");
break;
// length of line derivative is constant
// and we precompute it in the constructor
return xCoeff[0];
case kCubic_SegType:
x = (xCoeff[0]*ts + xCoeff[1])*ts + xCoeff[2];
y = (yCoeff[0]*ts + yCoeff[1])*ts + yCoeff[2];
break;
case kConic_SegType:
SkDebugf("Unimplemented");
UNIMPLEMENTED;
break;
default:
SkDebugf("Unimplemented");
UNIMPLEMENTED;
}
x = x * x;
@ -40,6 +97,7 @@ static inline Sk8f evaluateDerivativeLength(const Sk8f& ts,
return (x + y).sqrt();
}
ArcLengthIntegrator::ArcLengthIntegrator(const SkPoint* pts, SkSegType segType)
: fSegType(segType) {
switch (fSegType) {
@ -59,8 +117,13 @@ ArcLengthIntegrator::ArcLengthIntegrator(const SkPoint* pts, SkSegType segType)
yCoeff[1] = Sk8f(2.0f*(By - Ay));
}
break;
case kLine_SegType:
SkDEBUGF(("Unimplemented"));
case kLine_SegType: {
// the length of the derivative of a line is constant
// we put in in both coeff arrays for consistency's sake
SkScalar length = (pts[1] - pts[0]).length();
xCoeff[0] = Sk8f(length);
yCoeff[0] = Sk8f(length);
}
break;
case kCubic_SegType:
{
@ -73,6 +136,7 @@ ArcLengthIntegrator::ArcLengthIntegrator(const SkPoint* pts, SkSegType segType)
float Cy = pts[2].y();
float Dy = pts[3].y();
// precompute coefficients for derivative
xCoeff[0] = Sk8f(3.0f*(-Ax + 3.0f*(Bx - Cx) + Dx));
xCoeff[1] = Sk8f(3.0f*(2.0f*(Ax - 2.0f*Bx + Cx)));
xCoeff[2] = Sk8f(3.0f*(-Ax + Bx));
@ -83,10 +147,10 @@ ArcLengthIntegrator::ArcLengthIntegrator(const SkPoint* pts, SkSegType segType)
}
break;
case kConic_SegType:
SkDEBUGF(("Unimplemented"));
UNIMPLEMENTED;
break;
default:
SkDEBUGF(("Unimplemented"));
UNIMPLEMENTED;
}
}
@ -117,7 +181,8 @@ SkCurveMeasure::SkCurveMeasure(const SkPoint* pts, SkSegType segType)
}
break;
case SkSegType::kLine_SegType:
SkDebugf("Unimplemented");
fPts[0] = pts[0];
fPts[1] = pts[1];
break;
case SkSegType::kCubic_SegType:
for (size_t i = 0; i < 4; i++) {
@ -125,10 +190,12 @@ SkCurveMeasure::SkCurveMeasure(const SkPoint* pts, SkSegType segType)
}
break;
case SkSegType::kConic_SegType:
SkDebugf("Unimplemented");
for (size_t i = 0; i < 4; i++) {
fPts[i] = pts[i];
}
break;
default:
SkDEBUGF(("Unimplemented"));
UNIMPLEMENTED;
break;
}
fIntegrator = ArcLengthIntegrator(fPts, fSegType);
@ -199,9 +266,8 @@ SkScalar SkCurveMeasure::getTime(SkScalar targetLength) {
prevT = currentT;
if (iterations < kNewtonIters) {
// TODO(hstern) switch here on curve type.
// This is just newton's formula.
SkScalar dt = evaluateQuadDerivative(currentT).length();
SkScalar dt = evaluateDerivative(fPts, fSegType, currentT).length();
newT = currentT - (lengthDiff / dt);
// If newT is out of bounds, bisect inside newton.
@ -218,7 +284,7 @@ SkScalar SkCurveMeasure::getTime(SkScalar targetLength) {
newT = (minT + maxT) * 0.5f;
} else {
SkDEBUGF(("%.7f %.7f didn't get close enough after bisection.\n",
currentT, currentLength));
currentT, currentLength));
break;
}
currentT = newT;
@ -235,52 +301,16 @@ SkScalar SkCurveMeasure::getTime(SkScalar targetLength) {
}
void SkCurveMeasure::getPosTanTime(SkScalar targetLength, SkPoint* pos,
SkVector* tan, SkScalar* time) {
SkVector* tan, SkScalar* time) {
SkScalar t = getTime(targetLength);
if (time) {
*time = t;
}
if (pos) {
// TODO(hstern) switch here on curve type.
*pos = evaluateQuad(t);
*pos = evaluate(fPts, fSegType, t);
}
if (tan) {
// TODO(hstern) switch here on curve type.
*tan = evaluateQuadDerivative(t);
*tan = evaluateDerivative(fPts, fSegType, t);
}
}
// this is why I feel that the ArcLengthIntegrator should be combined
// with some sort of evaluator that caches the constants computed from the
// control points. this is basically the same code in ArcLengthIntegrator
SkPoint SkCurveMeasure::evaluateQuad(SkScalar t) {
SkScalar ti = 1.0f - t;
SkScalar Ax = fPts[0].x();
SkScalar Bx = fPts[1].x();
SkScalar Cx = fPts[2].x();
SkScalar Ay = fPts[0].y();
SkScalar By = fPts[1].y();
SkScalar Cy = fPts[2].y();
SkScalar x = Ax*ti*ti + 2.0f*Bx*t*ti + Cx*t*t;
SkScalar y = Ay*ti*ti + 2.0f*By*t*ti + Cy*t*t;
return SkPoint::Make(x, y);
}
SkVector SkCurveMeasure::evaluateQuadDerivative(SkScalar t) {
SkScalar Ax = fPts[0].x();
SkScalar Bx = fPts[1].x();
SkScalar Cx = fPts[2].x();
SkScalar Ay = fPts[0].y();
SkScalar By = fPts[1].y();
SkScalar Cy = fPts[2].y();
SkScalar A2BCx = 2.0f*(Ax - 2*Bx + Cx);
SkScalar A2BCy = 2.0f*(Ay - 2*By + Cy);
SkScalar ABx = 2.0f*(Bx - Ax);
SkScalar ABy = 2.0f*(By - Ay);
return SkPoint::Make(A2BCx*t + ABx, A2BCy*t + ABy);
}

16
src/utils/SkCurveMeasure.h
View File

@ -44,6 +44,15 @@ private:
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);
@ -51,13 +60,6 @@ public:
SkScalar getLength();
private:
SkPoint evaluateQuad(SkScalar t);
SkVector evaluateQuadDerivative(SkScalar t);
//SkPoint evaluate_cubic(SkScalar t);
//SkVector evaluate_cubic_derivative(SkScalar t);
//SkPoint evaluate_conic(SkScalar t);
//SkVector evaluate_conic_derivative(SkScalar t);
const SkScalar kTolerance = 0.0001f;
const int kNewtonIters = 5;
const int kBisectIters = 5;