| /* | |
| * Copyright 2011 Google Inc. | |
| * | |
| * Use of this source code is governed by a BSD-style license that can be | |
| * found in the LICENSE file. | |
| */ | |
| #include "GrPathUtils.h" | |
| #include "GrTypes.h" | |
| #include "SkMathPriv.h" | |
| #include "SkPointPriv.h" | |
| static const SkScalar gMinCurveTol = 0.0001f; | |
| SkScalar GrPathUtils::scaleToleranceToSrc(SkScalar devTol, | |
| const SkMatrix& viewM, | |
| const SkRect& pathBounds) { | |
| // In order to tesselate the path we get a bound on how much the matrix can | |
| // scale when mapping to screen coordinates. | |
| SkScalar stretch = viewM.getMaxScale(); | |
| if (stretch < 0) { | |
| // take worst case mapRadius amoung four corners. | |
| // (less than perfect) | |
| for (int i = 0; i < 4; ++i) { | |
| SkMatrix mat; | |
| mat.setTranslate((i % 2) ? pathBounds.fLeft : pathBounds.fRight, | |
| (i < 2) ? pathBounds.fTop : pathBounds.fBottom); | |
| mat.postConcat(viewM); | |
| stretch = SkMaxScalar(stretch, mat.mapRadius(SK_Scalar1)); | |
| } | |
| } | |
| SkScalar srcTol = 0; | |
| if (stretch <= 0) { | |
| // We have degenerate bounds or some degenerate matrix. Thus we set the tolerance to be the | |
| // max of the path pathBounds width and height. | |
| srcTol = SkTMax(pathBounds.width(), pathBounds.height()); | |
| } else { | |
| srcTol = devTol / stretch; | |
| } | |
| if (srcTol < gMinCurveTol) { | |
| srcTol = gMinCurveTol; | |
| } | |
| return srcTol; | |
| } | |
| uint32_t GrPathUtils::quadraticPointCount(const SkPoint points[], SkScalar tol) { | |
| // You should have called scaleToleranceToSrc, which guarantees this | |
| SkASSERT(tol >= gMinCurveTol); | |
| SkScalar d = SkPointPriv::DistanceToLineSegmentBetween(points[1], points[0], points[2]); | |
| if (!SkScalarIsFinite(d)) { | |
| return kMaxPointsPerCurve; | |
| } else if (d <= tol) { | |
| return 1; | |
| } else { | |
| // Each time we subdivide, d should be cut in 4. So we need to | |
| // subdivide x = log4(d/tol) times. x subdivisions creates 2^(x) | |
| // points. | |
| // 2^(log4(x)) = sqrt(x); | |
| SkScalar divSqrt = SkScalarSqrt(d / tol); | |
| if (((SkScalar)SK_MaxS32) <= divSqrt) { | |
| return kMaxPointsPerCurve; | |
| } else { | |
| int temp = SkScalarCeilToInt(divSqrt); | |
| int pow2 = GrNextPow2(temp); | |
| // Because of NaNs & INFs we can wind up with a degenerate temp | |
| // such that pow2 comes out negative. Also, our point generator | |
| // will always output at least one pt. | |
| if (pow2 < 1) { | |
| pow2 = 1; | |
| } | |
| return SkTMin(pow2, kMaxPointsPerCurve); | |
| } | |
| } | |
| } | |
| uint32_t GrPathUtils::generateQuadraticPoints(const SkPoint& p0, | |
| const SkPoint& p1, | |
| const SkPoint& p2, | |
| SkScalar tolSqd, | |
| SkPoint** points, | |
| uint32_t pointsLeft) { | |
| if (pointsLeft < 2 || | |
| (SkPointPriv::DistanceToLineSegmentBetweenSqd(p1, p0, p2)) < tolSqd) { | |
| (*points)[0] = p2; | |
| *points += 1; | |
| return 1; | |
| } | |
| SkPoint q[] = { | |
| { SkScalarAve(p0.fX, p1.fX), SkScalarAve(p0.fY, p1.fY) }, | |
| { SkScalarAve(p1.fX, p2.fX), SkScalarAve(p1.fY, p2.fY) }, | |
| }; | |
| SkPoint r = { SkScalarAve(q[0].fX, q[1].fX), SkScalarAve(q[0].fY, q[1].fY) }; | |
| pointsLeft >>= 1; | |
| uint32_t a = generateQuadraticPoints(p0, q[0], r, tolSqd, points, pointsLeft); | |
| uint32_t b = generateQuadraticPoints(r, q[1], p2, tolSqd, points, pointsLeft); | |
| return a + b; | |
| } | |
| uint32_t GrPathUtils::cubicPointCount(const SkPoint points[], | |
| SkScalar tol) { | |
| // You should have called scaleToleranceToSrc, which guarantees this | |
| SkASSERT(tol >= gMinCurveTol); | |
| SkScalar d = SkTMax( | |
| SkPointPriv::DistanceToLineSegmentBetweenSqd(points[1], points[0], points[3]), | |
| SkPointPriv::DistanceToLineSegmentBetweenSqd(points[2], points[0], points[3])); | |
| d = SkScalarSqrt(d); | |
| if (!SkScalarIsFinite(d)) { | |
| return kMaxPointsPerCurve; | |
| } else if (d <= tol) { | |
| return 1; | |
| } else { | |
| SkScalar divSqrt = SkScalarSqrt(d / tol); | |
| if (((SkScalar)SK_MaxS32) <= divSqrt) { | |
| return kMaxPointsPerCurve; | |
| } else { | |
| int temp = SkScalarCeilToInt(SkScalarSqrt(d / tol)); | |
| int pow2 = GrNextPow2(temp); | |
| // Because of NaNs & INFs we can wind up with a degenerate temp | |
| // such that pow2 comes out negative. Also, our point generator | |
| // will always output at least one pt. | |
| if (pow2 < 1) { | |
| pow2 = 1; | |
| } | |
| return SkTMin(pow2, kMaxPointsPerCurve); | |
| } | |
| } | |
| } | |
| uint32_t GrPathUtils::generateCubicPoints(const SkPoint& p0, | |
| const SkPoint& p1, | |
| const SkPoint& p2, | |
| const SkPoint& p3, | |
| SkScalar tolSqd, | |
| SkPoint** points, | |
| uint32_t pointsLeft) { | |
| if (pointsLeft < 2 || | |
| (SkPointPriv::DistanceToLineSegmentBetweenSqd(p1, p0, p3) < tolSqd && | |
| SkPointPriv::DistanceToLineSegmentBetweenSqd(p2, p0, p3) < tolSqd)) { | |
| (*points)[0] = p3; | |
| *points += 1; | |
| return 1; | |
| } | |
| SkPoint q[] = { | |
| { SkScalarAve(p0.fX, p1.fX), SkScalarAve(p0.fY, p1.fY) }, | |
| { SkScalarAve(p1.fX, p2.fX), SkScalarAve(p1.fY, p2.fY) }, | |
| { SkScalarAve(p2.fX, p3.fX), SkScalarAve(p2.fY, p3.fY) } | |
| }; | |
| SkPoint r[] = { | |
| { SkScalarAve(q[0].fX, q[1].fX), SkScalarAve(q[0].fY, q[1].fY) }, | |
| { SkScalarAve(q[1].fX, q[2].fX), SkScalarAve(q[1].fY, q[2].fY) } | |
| }; | |
| SkPoint s = { SkScalarAve(r[0].fX, r[1].fX), SkScalarAve(r[0].fY, r[1].fY) }; | |
| pointsLeft >>= 1; | |
| uint32_t a = generateCubicPoints(p0, q[0], r[0], s, tolSqd, points, pointsLeft); | |
| uint32_t b = generateCubicPoints(s, r[1], q[2], p3, tolSqd, points, pointsLeft); | |
| return a + b; | |
| } | |
| int GrPathUtils::worstCasePointCount(const SkPath& path, int* subpaths, SkScalar tol) { | |
| // You should have called scaleToleranceToSrc, which guarantees this | |
| SkASSERT(tol >= gMinCurveTol); | |
| int pointCount = 0; | |
| *subpaths = 1; | |
| bool first = true; | |
| SkPath::Iter iter(path, false); | |
| SkPath::Verb verb; | |
| SkPoint pts[4]; | |
| while ((verb = iter.next(pts, false)) != SkPath::kDone_Verb) { | |
| switch (verb) { | |
| case SkPath::kLine_Verb: | |
| pointCount += 1; | |
| break; | |
| case SkPath::kConic_Verb: { | |
| SkScalar weight = iter.conicWeight(); | |
| SkAutoConicToQuads converter; | |
| const SkPoint* quadPts = converter.computeQuads(pts, weight, tol); | |
| for (int i = 0; i < converter.countQuads(); ++i) { | |
| pointCount += quadraticPointCount(quadPts + 2*i, tol); | |
| } | |
| } | |
| case SkPath::kQuad_Verb: | |
| pointCount += quadraticPointCount(pts, tol); | |
| break; | |
| case SkPath::kCubic_Verb: | |
| pointCount += cubicPointCount(pts, tol); | |
| break; | |
| case SkPath::kMove_Verb: | |
| pointCount += 1; | |
| if (!first) { | |
| ++(*subpaths); | |
| } | |
| break; | |
| default: | |
| break; | |
| } | |
| first = false; | |
| } | |
| return pointCount; | |
| } | |
| void GrPathUtils::QuadUVMatrix::set(const SkPoint qPts[3]) { | |
| SkMatrix m; | |
| // We want M such that M * xy_pt = uv_pt | |
| // We know M * control_pts = [0 1/2 1] | |
| // [0 0 1] | |
| // [1 1 1] | |
| // And control_pts = [x0 x1 x2] | |
| // [y0 y1 y2] | |
| // [1 1 1 ] | |
| // We invert the control pt matrix and post concat to both sides to get M. | |
| // Using the known form of the control point matrix and the result, we can | |
| // optimize and improve precision. | |
| double x0 = qPts[0].fX; | |
| double y0 = qPts[0].fY; | |
| double x1 = qPts[1].fX; | |
| double y1 = qPts[1].fY; | |
| double x2 = qPts[2].fX; | |
| double y2 = qPts[2].fY; | |
| double det = x0*y1 - y0*x1 + x2*y0 - y2*x0 + x1*y2 - y1*x2; | |
| if (!sk_float_isfinite(det) | |
| || SkScalarNearlyZero((float)det, SK_ScalarNearlyZero * SK_ScalarNearlyZero)) { | |
| // The quad is degenerate. Hopefully this is rare. Find the pts that are | |
| // farthest apart to compute a line (unless it is really a pt). | |
| SkScalar maxD = SkPointPriv::DistanceToSqd(qPts[0], qPts[1]); | |
| int maxEdge = 0; | |
| SkScalar d = SkPointPriv::DistanceToSqd(qPts[1], qPts[2]); | |
| if (d > maxD) { | |
| maxD = d; | |
| maxEdge = 1; | |
| } | |
| d = SkPointPriv::DistanceToSqd(qPts[2], qPts[0]); | |
| if (d > maxD) { | |
| maxD = d; | |
| maxEdge = 2; | |
| } | |
| // We could have a tolerance here, not sure if it would improve anything | |
| if (maxD > 0) { | |
| // Set the matrix to give (u = 0, v = distance_to_line) | |
| SkVector lineVec = qPts[(maxEdge + 1)%3] - qPts[maxEdge]; | |
| // when looking from the point 0 down the line we want positive | |
| // distances to be to the left. This matches the non-degenerate | |
| // case. | |
| SkPointPriv::SetOrthog(&lineVec, lineVec, SkPointPriv::kLeft_Side); | |
| // first row | |
| fM[0] = 0; | |
| fM[1] = 0; | |
| fM[2] = 0; | |
| // second row | |
| fM[3] = lineVec.fX; | |
| fM[4] = lineVec.fY; | |
| fM[5] = -lineVec.dot(qPts[maxEdge]); | |
| } else { | |
| // It's a point. It should cover zero area. Just set the matrix such | |
| // that (u, v) will always be far away from the quad. | |
| fM[0] = 0; fM[1] = 0; fM[2] = 100.f; | |
| fM[3] = 0; fM[4] = 0; fM[5] = 100.f; | |
| } | |
| } else { | |
| double scale = 1.0/det; | |
| // compute adjugate matrix | |
| double a2, a3, a4, a5, a6, a7, a8; | |
| a2 = x1*y2-x2*y1; | |
| a3 = y2-y0; | |
| a4 = x0-x2; | |
| a5 = x2*y0-x0*y2; | |
| a6 = y0-y1; | |
| a7 = x1-x0; | |
| a8 = x0*y1-x1*y0; | |
| // this performs the uv_pts*adjugate(control_pts) multiply, | |
| // then does the scale by 1/det afterwards to improve precision | |
| m[SkMatrix::kMScaleX] = (float)((0.5*a3 + a6)*scale); | |
| m[SkMatrix::kMSkewX] = (float)((0.5*a4 + a7)*scale); | |
| m[SkMatrix::kMTransX] = (float)((0.5*a5 + a8)*scale); | |
| m[SkMatrix::kMSkewY] = (float)(a6*scale); | |
| m[SkMatrix::kMScaleY] = (float)(a7*scale); | |
| m[SkMatrix::kMTransY] = (float)(a8*scale); | |
| // kMPersp0 & kMPersp1 should algebraically be zero | |
| m[SkMatrix::kMPersp0] = 0.0f; | |
| m[SkMatrix::kMPersp1] = 0.0f; | |
| m[SkMatrix::kMPersp2] = (float)((a2 + a5 + a8)*scale); | |
| // It may not be normalized to have 1.0 in the bottom right | |
| float m33 = m.get(SkMatrix::kMPersp2); | |
| if (1.f != m33) { | |
| m33 = 1.f / m33; | |
| fM[0] = m33 * m.get(SkMatrix::kMScaleX); | |
| fM[1] = m33 * m.get(SkMatrix::kMSkewX); | |
| fM[2] = m33 * m.get(SkMatrix::kMTransX); | |
| fM[3] = m33 * m.get(SkMatrix::kMSkewY); | |
| fM[4] = m33 * m.get(SkMatrix::kMScaleY); | |
| fM[5] = m33 * m.get(SkMatrix::kMTransY); | |
| } else { | |
| fM[0] = m.get(SkMatrix::kMScaleX); | |
| fM[1] = m.get(SkMatrix::kMSkewX); | |
| fM[2] = m.get(SkMatrix::kMTransX); | |
| fM[3] = m.get(SkMatrix::kMSkewY); | |
| fM[4] = m.get(SkMatrix::kMScaleY); | |
| fM[5] = m.get(SkMatrix::kMTransY); | |
| } | |
| } | |
| } | |
| //////////////////////////////////////////////////////////////////////////////// | |
| // k = (y2 - y0, x0 - x2, x2*y0 - x0*y2) | |
| // l = (y1 - y0, x0 - x1, x1*y0 - x0*y1) * 2*w | |
| // m = (y2 - y1, x1 - x2, x2*y1 - x1*y2) * 2*w | |
| void GrPathUtils::getConicKLM(const SkPoint p[3], const SkScalar weight, SkMatrix* out) { | |
| SkMatrix& klm = *out; | |
| const SkScalar w2 = 2.f * weight; | |
| klm[0] = p[2].fY - p[0].fY; | |
| klm[1] = p[0].fX - p[2].fX; | |
| klm[2] = p[2].fX * p[0].fY - p[0].fX * p[2].fY; | |
| klm[3] = w2 * (p[1].fY - p[0].fY); | |
| klm[4] = w2 * (p[0].fX - p[1].fX); | |
| klm[5] = w2 * (p[1].fX * p[0].fY - p[0].fX * p[1].fY); | |
| klm[6] = w2 * (p[2].fY - p[1].fY); | |
| klm[7] = w2 * (p[1].fX - p[2].fX); | |
| klm[8] = w2 * (p[2].fX * p[1].fY - p[1].fX * p[2].fY); | |
| // scale the max absolute value of coeffs to 10 | |
| SkScalar scale = 0.f; | |
| for (int i = 0; i < 9; ++i) { | |
| scale = SkMaxScalar(scale, SkScalarAbs(klm[i])); | |
| } | |
| SkASSERT(scale > 0.f); | |
| scale = 10.f / scale; | |
| for (int i = 0; i < 9; ++i) { | |
| klm[i] *= scale; | |
| } | |
| } | |
| //////////////////////////////////////////////////////////////////////////////// | |
| namespace { | |
| // a is the first control point of the cubic. | |
| // ab is the vector from a to the second control point. | |
| // dc is the vector from the fourth to the third control point. | |
| // d is the fourth control point. | |
| // p is the candidate quadratic control point. | |
| // this assumes that the cubic doesn't inflect and is simple | |
| bool is_point_within_cubic_tangents(const SkPoint& a, | |
| const SkVector& ab, | |
| const SkVector& dc, | |
| const SkPoint& d, | |
| SkPathPriv::FirstDirection dir, | |
| const SkPoint p) { | |
| SkVector ap = p - a; | |
| SkScalar apXab = ap.cross(ab); | |
| if (SkPathPriv::kCW_FirstDirection == dir) { | |
| if (apXab > 0) { | |
| return false; | |
| } | |
| } else { | |
| SkASSERT(SkPathPriv::kCCW_FirstDirection == dir); | |
| if (apXab < 0) { | |
| return false; | |
| } | |
| } | |
| SkVector dp = p - d; | |
| SkScalar dpXdc = dp.cross(dc); | |
| if (SkPathPriv::kCW_FirstDirection == dir) { | |
| if (dpXdc < 0) { | |
| return false; | |
| } | |
| } else { | |
| SkASSERT(SkPathPriv::kCCW_FirstDirection == dir); | |
| if (dpXdc > 0) { | |
| return false; | |
| } | |
| } | |
| return true; | |
| } | |
| void convert_noninflect_cubic_to_quads(const SkPoint p[4], | |
| SkScalar toleranceSqd, | |
| bool constrainWithinTangents, | |
| SkPathPriv::FirstDirection dir, | |
| SkTArray<SkPoint, true>* quads, | |
| int sublevel = 0) { | |
| // Notation: Point a is always p[0]. Point b is p[1] unless p[1] == p[0], in which case it is | |
| // p[2]. Point d is always p[3]. Point c is p[2] unless p[2] == p[3], in which case it is p[1]. | |
| SkVector ab = p[1] - p[0]; | |
| SkVector dc = p[2] - p[3]; | |
| if (SkPointPriv::LengthSqd(ab) < SK_ScalarNearlyZero) { | |
| if (SkPointPriv::LengthSqd(dc) < SK_ScalarNearlyZero) { | |
| SkPoint* degQuad = quads->push_back_n(3); | |
| degQuad[0] = p[0]; | |
| degQuad[1] = p[0]; | |
| degQuad[2] = p[3]; | |
| return; | |
| } | |
| ab = p[2] - p[0]; | |
| } | |
| if (SkPointPriv::LengthSqd(dc) < SK_ScalarNearlyZero) { | |
| dc = p[1] - p[3]; | |
| } | |
| // When the ab and cd tangents are degenerate or nearly parallel with vector from d to a the | |
| // constraint that the quad point falls between the tangents becomes hard to enforce and we are | |
| // likely to hit the max subdivision count. However, in this case the cubic is approaching a | |
| // line and the accuracy of the quad point isn't so important. We check if the two middle cubic | |
| // control points are very close to the baseline vector. If so then we just pick quadratic | |
| // points on the control polygon. | |
| if (constrainWithinTangents) { | |
| SkVector da = p[0] - p[3]; | |
| bool doQuads = SkPointPriv::LengthSqd(dc) < SK_ScalarNearlyZero || | |
| SkPointPriv::LengthSqd(ab) < SK_ScalarNearlyZero; | |
| if (!doQuads) { | |
| SkScalar invDALengthSqd = SkPointPriv::LengthSqd(da); | |
| if (invDALengthSqd > SK_ScalarNearlyZero) { | |
| invDALengthSqd = SkScalarInvert(invDALengthSqd); | |
| // cross(ab, da)^2/length(da)^2 == sqd distance from b to line from d to a. | |
| // same goes for point c using vector cd. | |
| SkScalar detABSqd = ab.cross(da); | |
| detABSqd = SkScalarSquare(detABSqd); | |
| SkScalar detDCSqd = dc.cross(da); | |
| detDCSqd = SkScalarSquare(detDCSqd); | |
| if (detABSqd * invDALengthSqd < toleranceSqd && | |
| detDCSqd * invDALengthSqd < toleranceSqd) | |
| { | |
| doQuads = true; | |
| } | |
| } | |
| } | |
| if (doQuads) { | |
| SkPoint b = p[0] + ab; | |
| SkPoint c = p[3] + dc; | |
| SkPoint mid = b + c; | |
| mid.scale(SK_ScalarHalf); | |
| // Insert two quadratics to cover the case when ab points away from d and/or dc | |
| // points away from a. | |
| if (SkVector::DotProduct(da, dc) < 0 || SkVector::DotProduct(ab,da) > 0) { | |
| SkPoint* qpts = quads->push_back_n(6); | |
| qpts[0] = p[0]; | |
| qpts[1] = b; | |
| qpts[2] = mid; | |
| qpts[3] = mid; | |
| qpts[4] = c; | |
| qpts[5] = p[3]; | |
| } else { | |
| SkPoint* qpts = quads->push_back_n(3); | |
| qpts[0] = p[0]; | |
| qpts[1] = mid; | |
| qpts[2] = p[3]; | |
| } | |
| return; | |
| } | |
| } | |
| static const SkScalar kLengthScale = 3 * SK_Scalar1 / 2; | |
| static const int kMaxSubdivs = 10; | |
| ab.scale(kLengthScale); | |
| dc.scale(kLengthScale); | |
| // e0 and e1 are extrapolations along vectors ab and dc. | |
| SkVector c0 = p[0]; | |
| c0 += ab; | |
| SkVector c1 = p[3]; | |
| c1 += dc; | |
| SkScalar dSqd = sublevel > kMaxSubdivs ? 0 : SkPointPriv::DistanceToSqd(c0, c1); | |
| if (dSqd < toleranceSqd) { | |
| SkPoint cAvg = c0; | |
| cAvg += c1; | |
| cAvg.scale(SK_ScalarHalf); | |
| bool subdivide = false; | |
| if (constrainWithinTangents && | |
| !is_point_within_cubic_tangents(p[0], ab, dc, p[3], dir, cAvg)) { | |
| // choose a new cAvg that is the intersection of the two tangent lines. | |
| SkPointPriv::SetOrthog(&ab, ab); | |
| SkScalar z0 = -ab.dot(p[0]); | |
| SkPointPriv::SetOrthog(&dc, dc); | |
| SkScalar z1 = -dc.dot(p[3]); | |
| cAvg.fX = ab.fY * z1 - z0 * dc.fY; | |
| cAvg.fY = z0 * dc.fX - ab.fX * z1; | |
| SkScalar z = ab.fX * dc.fY - ab.fY * dc.fX; | |
| z = SkScalarInvert(z); | |
| cAvg.fX *= z; | |
| cAvg.fY *= z; | |
| if (sublevel <= kMaxSubdivs) { | |
| SkScalar d0Sqd = SkPointPriv::DistanceToSqd(c0, cAvg); | |
| SkScalar d1Sqd = SkPointPriv::DistanceToSqd(c1, cAvg); | |
| // We need to subdivide if d0 + d1 > tolerance but we have the sqd values. We know | |
| // the distances and tolerance can't be negative. | |
| // (d0 + d1)^2 > toleranceSqd | |
| // d0Sqd + 2*d0*d1 + d1Sqd > toleranceSqd | |
| SkScalar d0d1 = SkScalarSqrt(d0Sqd * d1Sqd); | |
| subdivide = 2 * d0d1 + d0Sqd + d1Sqd > toleranceSqd; | |
| } | |
| } | |
| if (!subdivide) { | |
| SkPoint* pts = quads->push_back_n(3); | |
| pts[0] = p[0]; | |
| pts[1] = cAvg; | |
| pts[2] = p[3]; | |
| return; | |
| } | |
| } | |
| SkPoint choppedPts[7]; | |
| SkChopCubicAtHalf(p, choppedPts); | |
| convert_noninflect_cubic_to_quads(choppedPts + 0, | |
| toleranceSqd, | |
| constrainWithinTangents, | |
| dir, | |
| quads, | |
| sublevel + 1); | |
| convert_noninflect_cubic_to_quads(choppedPts + 3, | |
| toleranceSqd, | |
| constrainWithinTangents, | |
| dir, | |
| quads, | |
| sublevel + 1); | |
| } | |
| } | |
| void GrPathUtils::convertCubicToQuads(const SkPoint p[4], | |
| SkScalar tolScale, | |
| SkTArray<SkPoint, true>* quads) { | |
| if (!p[0].isFinite() || !p[1].isFinite() || !p[2].isFinite() || !p[3].isFinite()) { | |
| return; | |
| } | |
| if (!SkScalarIsFinite(tolScale)) { | |
| return; | |
| } | |
| SkPoint chopped[10]; | |
| int count = SkChopCubicAtInflections(p, chopped); | |
| const SkScalar tolSqd = SkScalarSquare(tolScale); | |
| for (int i = 0; i < count; ++i) { | |
| SkPoint* cubic = chopped + 3*i; | |
| // The direction param is ignored if the third param is false. | |
| convert_noninflect_cubic_to_quads(cubic, tolSqd, false, | |
| SkPathPriv::kCCW_FirstDirection, quads); | |
| } | |
| } | |
| void GrPathUtils::convertCubicToQuadsConstrainToTangents(const SkPoint p[4], | |
| SkScalar tolScale, | |
| SkPathPriv::FirstDirection dir, | |
| SkTArray<SkPoint, true>* quads) { | |
| if (!p[0].isFinite() || !p[1].isFinite() || !p[2].isFinite() || !p[3].isFinite()) { | |
| return; | |
| } | |
| if (!SkScalarIsFinite(tolScale)) { | |
| return; | |
| } | |
| SkPoint chopped[10]; | |
| int count = SkChopCubicAtInflections(p, chopped); | |
| const SkScalar tolSqd = SkScalarSquare(tolScale); | |
| for (int i = 0; i < count; ++i) { | |
| SkPoint* cubic = chopped + 3*i; | |
| convert_noninflect_cubic_to_quads(cubic, tolSqd, true, dir, quads); | |
| } | |
| } | |
| //////////////////////////////////////////////////////////////////////////////// | |
| using ExcludedTerm = GrPathUtils::ExcludedTerm; | |
| ExcludedTerm GrPathUtils::calcCubicInverseTransposePowerBasisMatrix(const SkPoint p[4], | |
| SkMatrix* out) { | |
| GR_STATIC_ASSERT(SK_SCALAR_IS_FLOAT); | |
| // First convert the bezier coordinates p[0..3] to power basis coefficients X,Y(,W=[0 0 0 1]). | |
| // M3 is the matrix that does this conversion. The homogeneous equation for the cubic becomes: | |
| // | |
| // | X Y 0 | | |
| // C(t,s) = [t^3 t^2*s t*s^2 s^3] * | . . 0 | | |
| // | . . 0 | | |
| // | . . 1 | | |
| // | |
| const Sk4f M3[3] = {Sk4f(-1, 3, -3, 1), | |
| Sk4f(3, -6, 3, 0), | |
| Sk4f(-3, 3, 0, 0)}; | |
| // 4th col of M3 = Sk4f(1, 0, 0, 0)}; | |
| Sk4f X(p[3].x(), 0, 0, 0); | |
| Sk4f Y(p[3].y(), 0, 0, 0); | |
| for (int i = 2; i >= 0; --i) { | |
| X += M3[i] * p[i].x(); | |
| Y += M3[i] * p[i].y(); | |
| } | |
| // The matrix is 3x4. In order to invert it, we first need to make it square by throwing out one | |
| // of the middle two rows. We toss the row that leaves us with the largest absolute determinant. | |
| // Since the right column will be [0 0 1], the respective determinants reduce to x0*y2 - y0*x2 | |
| // and x0*y1 - y0*x1. | |
| SkScalar dets[4]; | |
| Sk4f D = SkNx_shuffle<0,0,2,1>(X) * SkNx_shuffle<2,1,0,0>(Y); | |
| D -= SkNx_shuffle<2,3,0,1>(D); | |
| D.store(dets); | |
| ExcludedTerm skipTerm = SkScalarAbs(dets[0]) > SkScalarAbs(dets[1]) ? | |
| ExcludedTerm::kQuadraticTerm : ExcludedTerm::kLinearTerm; | |
| SkScalar det = dets[ExcludedTerm::kQuadraticTerm == skipTerm ? 0 : 1]; | |
| if (0 == det) { | |
| return ExcludedTerm::kNonInvertible; | |
| } | |
| SkScalar rdet = 1 / det; | |
| // Compute the inverse-transpose of the power basis matrix with the 'skipRow'th row removed. | |
| // Since W=[0 0 0 1], it follows that our corresponding solution will be equal to: | |
| // | |
| // | y1 -x1 x1*y2 - y1*x2 | | |
| // 1/det * | -y0 x0 -x0*y2 + y0*x2 | | |
| // | 0 0 det | | |
| // | |
| SkScalar x[4], y[4], z[4]; | |
| X.store(x); | |
| Y.store(y); | |
| (X * SkNx_shuffle<3,3,3,3>(Y) - Y * SkNx_shuffle<3,3,3,3>(X)).store(z); | |
| int middleRow = ExcludedTerm::kQuadraticTerm == skipTerm ? 2 : 1; | |
| out->setAll( y[middleRow] * rdet, -x[middleRow] * rdet, z[middleRow] * rdet, | |
| -y[0] * rdet, x[0] * rdet, -z[0] * rdet, | |
| 0, 0, 1); | |
| return skipTerm; | |
| } | |
| inline static void calc_serp_kcoeffs(SkScalar tl, SkScalar sl, SkScalar tm, SkScalar sm, | |
| ExcludedTerm skipTerm, SkScalar outCoeffs[3]) { | |
| SkASSERT(ExcludedTerm::kQuadraticTerm == skipTerm || ExcludedTerm::kLinearTerm == skipTerm); | |
| outCoeffs[0] = 0; | |
| outCoeffs[1] = (ExcludedTerm::kLinearTerm == skipTerm) ? sl*sm : -tl*sm - tm*sl; | |
| outCoeffs[2] = tl*tm; | |
| } | |
| inline static void calc_serp_lmcoeffs(SkScalar t, SkScalar s, ExcludedTerm skipTerm, | |
| SkScalar outCoeffs[3]) { | |
| SkASSERT(ExcludedTerm::kQuadraticTerm == skipTerm || ExcludedTerm::kLinearTerm == skipTerm); | |
| outCoeffs[0] = -s*s*s; | |
| outCoeffs[1] = (ExcludedTerm::kLinearTerm == skipTerm) ? 3*s*s*t : -3*s*t*t; | |
| outCoeffs[2] = t*t*t; | |
| } | |
| inline static void calc_loop_kcoeffs(SkScalar td, SkScalar sd, SkScalar te, SkScalar se, | |
| SkScalar tdse, SkScalar tesd, ExcludedTerm skipTerm, | |
| SkScalar outCoeffs[3]) { | |
| SkASSERT(ExcludedTerm::kQuadraticTerm == skipTerm || ExcludedTerm::kLinearTerm == skipTerm); | |
| outCoeffs[0] = 0; | |
| outCoeffs[1] = (ExcludedTerm::kLinearTerm == skipTerm) ? sd*se : -tdse - tesd; | |
| outCoeffs[2] = td*te; | |
| } | |
| inline static void calc_loop_lmcoeffs(SkScalar t2, SkScalar s2, SkScalar t1, SkScalar s1, | |
| SkScalar t2s1, SkScalar t1s2, ExcludedTerm skipTerm, | |
| SkScalar outCoeffs[3]) { | |
| SkASSERT(ExcludedTerm::kQuadraticTerm == skipTerm || ExcludedTerm::kLinearTerm == skipTerm); | |
| outCoeffs[0] = -s2*s2*s1; | |
| outCoeffs[1] = (ExcludedTerm::kLinearTerm == skipTerm) ? s2 * (2*t2s1 + t1s2) | |
| : -t2 * (t2s1 + 2*t1s2); | |
| outCoeffs[2] = t2*t2*t1; | |
| } | |
| // For the case when a cubic bezier is actually a quadratic. We duplicate k in l so that the | |
| // implicit becomes: | |
| // | |
| // k^3 - l*m == k^3 - l*k == k * (k^2 - l) | |
| // | |
| // In the quadratic case we can simply assign fixed values at each control point: | |
| // | |
| // | ..K.. | | pts[0] pts[1] pts[2] pts[3] | | 0 1/3 2/3 1 | | |
| // | ..L.. | * | . . . . | == | 0 0 1/3 1 | | |
| // | ..K.. | | 1 1 1 1 | | 0 1/3 2/3 1 | | |
| // | |
| static void calc_quadratic_klm(const SkPoint pts[4], double d3, SkMatrix* klm) { | |
| SkMatrix klmAtPts; | |
| klmAtPts.setAll(0, 1.f/3, 1, | |
| 0, 0, 1, | |
| 0, 1.f/3, 1); | |
| SkMatrix inversePts; | |
| inversePts.setAll(pts[0].x(), pts[1].x(), pts[3].x(), | |
| pts[0].y(), pts[1].y(), pts[3].y(), | |
| 1, 1, 1); | |
| SkAssertResult(inversePts.invert(&inversePts)); | |
| klm->setConcat(klmAtPts, inversePts); | |
| // If d3 > 0 we need to flip the orientation of our curve | |
| // This is done by negating the k and l values | |
| if (d3 > 0) { | |
| klm->postScale(-1, -1); | |
| } | |
| } | |
| // For the case when a cubic bezier is actually a line. We set K=0, L=1, M=-line, which results in | |
| // the following implicit: | |
| // | |
| // k^3 - l*m == 0^3 - 1*(-line) == -(-line) == line | |
| // | |
| static void calc_line_klm(const SkPoint pts[4], SkMatrix* klm) { | |
| SkScalar ny = pts[0].x() - pts[3].x(); | |
| SkScalar nx = pts[3].y() - pts[0].y(); | |
| SkScalar k = nx * pts[0].x() + ny * pts[0].y(); | |
| klm->setAll( 0, 0, 0, | |
| 0, 0, 1, | |
| -nx, -ny, k); | |
| } | |
| SkCubicType GrPathUtils::getCubicKLM(const SkPoint src[4], SkMatrix* klm, double tt[2], | |
| double ss[2]) { | |
| double d[4]; | |
| SkCubicType type = SkClassifyCubic(src, tt, ss, d); | |
| if (SkCubicType::kLineOrPoint == type) { | |
| calc_line_klm(src, klm); | |
| return SkCubicType::kLineOrPoint; | |
| } | |
| if (SkCubicType::kQuadratic == type) { | |
| calc_quadratic_klm(src, d[3], klm); | |
| return SkCubicType::kQuadratic; | |
| } | |
| SkMatrix CIT; | |
| ExcludedTerm skipTerm = calcCubicInverseTransposePowerBasisMatrix(src, &CIT); | |
| if (ExcludedTerm::kNonInvertible == skipTerm) { | |
| // This could technically also happen if the curve were quadratic, but SkClassifyCubic | |
| // should have detected that case already with tolerance. | |
| calc_line_klm(src, klm); | |
| return SkCubicType::kLineOrPoint; | |
| } | |
| const SkScalar t0 = static_cast<SkScalar>(tt[0]), t1 = static_cast<SkScalar>(tt[1]), | |
| s0 = static_cast<SkScalar>(ss[0]), s1 = static_cast<SkScalar>(ss[1]); | |
| SkMatrix klmCoeffs; | |
| switch (type) { | |
| case SkCubicType::kCuspAtInfinity: | |
| SkASSERT(1 == t1 && 0 == s1); // Infinity. | |
| // fallthru. | |
| case SkCubicType::kLocalCusp: | |
| case SkCubicType::kSerpentine: | |
| calc_serp_kcoeffs(t0, s0, t1, s1, skipTerm, &klmCoeffs[0]); | |
| calc_serp_lmcoeffs(t0, s0, skipTerm, &klmCoeffs[3]); | |
| calc_serp_lmcoeffs(t1, s1, skipTerm, &klmCoeffs[6]); | |
| break; | |
| case SkCubicType::kLoop: { | |
| const SkScalar tdse = t0 * s1; | |
| const SkScalar tesd = t1 * s0; | |
| calc_loop_kcoeffs(t0, s0, t1, s1, tdse, tesd, skipTerm, &klmCoeffs[0]); | |
| calc_loop_lmcoeffs(t0, s0, t1, s1, tdse, tesd, skipTerm, &klmCoeffs[3]); | |
| calc_loop_lmcoeffs(t1, s1, t0, s0, tesd, tdse, skipTerm, &klmCoeffs[6]); | |
| break; | |
| } | |
| default: | |
| SK_ABORT("Unexpected cubic type."); | |
| break; | |
| } | |
| klm->setConcat(klmCoeffs, CIT); | |
| return type; | |
| } | |
| int GrPathUtils::chopCubicAtLoopIntersection(const SkPoint src[4], SkPoint dst[10], SkMatrix* klm, | |
| int* loopIndex) { | |
| SkSTArray<2, SkScalar> chops; | |
| *loopIndex = -1; | |
| double t[2], s[2]; | |
| if (SkCubicType::kLoop == GrPathUtils::getCubicKLM(src, klm, t, s)) { | |
| SkScalar t0 = static_cast<SkScalar>(t[0] / s[0]); | |
| SkScalar t1 = static_cast<SkScalar>(t[1] / s[1]); | |
| SkASSERT(t0 <= t1); // Technically t0 != t1 in a loop, but there may be FP error. | |
| if (t0 < 1 && t1 > 0) { | |
| *loopIndex = 0; | |
| if (t0 > 0) { | |
| chops.push_back(t0); | |
| *loopIndex = 1; | |
| } | |
| if (t1 < 1) { | |
| chops.push_back(t1); | |
| *loopIndex = chops.count() - 1; | |
| } | |
| } | |
| } | |
| SkChopCubicAt(src, dst, chops.begin(), chops.count()); | |
| return chops.count() + 1; | |
| } |