| /* |
| * Copyright 2020 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "imgui.h" |
| #include "include/core/SkBitmap.h" |
| #include "include/core/SkCanvas.h" |
| #include "include/core/SkPath.h" |
| #include "include/core/SkPathMeasure.h" |
| #include "include/utils/SkParsePath.h" |
| #include "samplecode/Sample.h" |
| |
| #include "src/core/SkGeometry.h" |
| |
| #include <stack> |
| |
| namespace { |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| constexpr inline SkPoint rotate90(const SkPoint& p) { return {p.fY, -p.fX}; } |
| inline SkPoint rotate180(const SkPoint& p) { return p * -1; } |
| inline bool isClockwise(const SkPoint& a, const SkPoint& b) { return a.cross(b) > 0; } |
| |
| static SkPoint checkSetLength(SkPoint p, float len, const char* file, int line) { |
| if (!p.setLength(len)) { |
| SkDebugf("%s:%d: Failed to set point length\n", file, line); |
| } |
| return p; |
| } |
| |
| /** Version of setLength that prints debug msg on failure to help catch edge cases */ |
| #define setLength(p, len) checkSetLength(p, len, __FILE__, __LINE__) |
| |
| constexpr uint64_t choose(uint64_t n, uint64_t k) { |
| SkASSERT(n >= k); |
| uint64_t result = 1; |
| for (uint64_t i = 1; i <= k; i++) { |
| result *= (n + 1 - i); |
| result /= i; |
| } |
| return result; |
| } |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| /** |
| * A scalar (float-valued weights) Bezier curve of arbitrary degree. |
| */ |
| class ScalarBezCurve { |
| public: |
| static constexpr int kDegreeInvalid = -1; |
| |
| /** Creates an empty curve with invalid degree. */ |
| ScalarBezCurve() : fDegree(kDegreeInvalid) {} |
| |
| /** Creates a curve of the specified degree with weights initialized to 0. */ |
| explicit ScalarBezCurve(int degree) : fDegree(degree) { |
| SkASSERT(degree >= 0); |
| fWeights.resize(degree + 1, {0}); |
| } |
| |
| /** Creates a curve of specified degree with the given weights. */ |
| ScalarBezCurve(int degree, const std::vector<float>& weights) : ScalarBezCurve(degree) { |
| SkASSERT(degree >= 0); |
| SkASSERT(weights.size() == (size_t)degree + 1); |
| fWeights.insert(fWeights.begin(), weights.begin(), weights.end()); |
| } |
| |
| /** Returns the extreme-valued weight */ |
| float extremumWeight() const { |
| float f = 0; |
| int sign = 1; |
| for (float w : fWeights) { |
| if (std::abs(w) > f) { |
| f = std::abs(w); |
| sign = w >= 0 ? 1 : -1; |
| } |
| } |
| return sign * f; |
| } |
| |
| /** Evaluates the curve at t */ |
| float eval(float t) const { return Eval(*this, t); } |
| |
| /** Evaluates the curve at t */ |
| static float Eval(const ScalarBezCurve& curve, float t) { |
| // Set up starting point of recursion (k=0) |
| ScalarBezCurve result = curve; |
| |
| for (int k = 1; k <= curve.fDegree; k++) { |
| // k is level of recursion, k-1 has previous level's values. |
| for (int i = curve.fDegree; i >= k; i--) { |
| result.fWeights[i] = result.fWeights[i - 1] * (1 - t) + result.fWeights[i] * t; |
| } |
| } |
| |
| return result.fWeights[curve.fDegree]; |
| } |
| |
| /** Splits this curve at t into two halves (of the same degree) */ |
| void split(float t, ScalarBezCurve* left, ScalarBezCurve* right) const { |
| Split(*this, t, left, right); |
| } |
| |
| /** Splits this curve into the subinterval [tmin,tmax]. */ |
| void split(float tmin, float tmax, ScalarBezCurve* result) const { |
| // TODO: I believe there's a more efficient algorithm for this |
| const float tRel = tmin / tmax; |
| ScalarBezCurve ll, rl, rr; |
| this->split(tmax, &rl, &rr); |
| rl.split(tRel, &ll, result); |
| } |
| |
| /** Splits the curve at t into two halves (of the same degree) */ |
| static void Split(const ScalarBezCurve& curve, |
| float t, |
| ScalarBezCurve* left, |
| ScalarBezCurve* right) { |
| // Set up starting point of recursion (k=0) |
| const int degree = curve.fDegree; |
| ScalarBezCurve result = curve; |
| *left = ScalarBezCurve(degree); |
| *right = ScalarBezCurve(degree); |
| left->fWeights[0] = curve.fWeights[0]; |
| right->fWeights[degree] = curve.fWeights[degree]; |
| |
| for (int k = 1; k <= degree; k++) { |
| // k is level of recursion, k-1 has previous level's values. |
| for (int i = degree; i >= k; i--) { |
| result.fWeights[i] = result.fWeights[i - 1] * (1 - t) + result.fWeights[i] * t; |
| } |
| |
| left->fWeights[k] = result.fWeights[k]; |
| right->fWeights[degree - k] = result.fWeights[degree]; |
| } |
| } |
| |
| /** |
| * Increases the degree of the curve to the given degree. Has no effect if the |
| * degree is already equal to the given degree. |
| * |
| * This process is always exact (NB the reverse, degree reduction, is not exact). |
| */ |
| void elevateDegree(int newDegree) { |
| if (newDegree == fDegree) { |
| return; |
| } |
| |
| fWeights = ElevateDegree(*this, newDegree).fWeights; |
| fDegree = newDegree; |
| } |
| |
| /** |
| * Increases the degree of the curve to the given degree. Has no effect if the |
| * degree is already equal to the given degree. |
| * |
| * This process is always exact (NB the reverse, degree reduction, is not exact). |
| */ |
| static ScalarBezCurve ElevateDegree(const ScalarBezCurve& curve, int newDegree) { |
| SkASSERT(newDegree >= curve.degree()); |
| if (newDegree == curve.degree()) { |
| return curve; |
| } |
| |
| // From Farouki, Rajan, "Algorithms for polynomials in Bernstein form" 1988. |
| ScalarBezCurve elevated(newDegree); |
| const int r = newDegree - curve.fDegree; |
| const int n = curve.fDegree; |
| |
| for (int i = 0; i <= n + r; i++) { |
| elevated.fWeights[i] = 0; |
| for (int j = std::max(0, i - r); j <= std::min(n, i); j++) { |
| const float f = |
| (choose(n, j) * choose(r, i - j)) / static_cast<float>(choose(n + r, i)); |
| elevated.fWeights[i] += curve.fWeights[j] * f; |
| } |
| } |
| |
| return elevated; |
| } |
| |
| /** |
| * Returns the zero-set of this curve, which is a list of t values where the curve crosses 0. |
| */ |
| std::vector<float> zeroSet() const { return ZeroSet(*this); } |
| |
| /** |
| * Returns the zero-set of the curve, which is a list of t values where the curve crosses 0. |
| */ |
| static std::vector<float> ZeroSet(const ScalarBezCurve& curve) { |
| constexpr float kTol = 0.001f; |
| std::vector<float> result; |
| ZeroSetRec(curve, 0, 1, kTol, &result); |
| return result; |
| } |
| |
| /** Multiplies the curve's weights by a constant value */ |
| static ScalarBezCurve Mul(const ScalarBezCurve& curve, float f) { |
| ScalarBezCurve result = curve; |
| for (int k = 0; k <= curve.fDegree; k++) { |
| result.fWeights[k] *= f; |
| } |
| return result; |
| } |
| |
| /** |
| * Multiplies the two curves and returns the result. |
| * |
| * Degree of resulting curve is the sum of the degrees of the input curves. |
| */ |
| static ScalarBezCurve Mul(const ScalarBezCurve& a, const ScalarBezCurve& b) { |
| // From G. Elber, "Free form surface analysis using a hybrid of symbolic and numeric |
| // computation". PhD thesis, 1992. p.11. |
| const int n = a.degree(), m = b.degree(); |
| const int newDegree = n + m; |
| ScalarBezCurve result(newDegree); |
| |
| for (int k = 0; k <= newDegree; k++) { |
| result.fWeights[k] = 0; |
| for (int i = std::max(0, k - n); i <= std::min(k, m); i++) { |
| const float f = |
| (choose(m, i) * choose(n, k - i)) / static_cast<float>(choose(m + n, k)); |
| result.fWeights[k] += a.fWeights[i] * b.fWeights[k - i] * f; |
| } |
| } |
| |
| return result; |
| } |
| |
| /** Returns a^2 + b^2. This is a specialized method because the loops are easily fused. */ |
| static ScalarBezCurve AddSquares(const ScalarBezCurve& a, const ScalarBezCurve& b) { |
| const int n = a.degree(), m = b.degree(); |
| const int newDegree = n + m; |
| ScalarBezCurve result(newDegree); |
| |
| for (int k = 0; k <= newDegree; k++) { |
| float aSq = 0, bSq = 0; |
| for (int i = std::max(0, k - n); i <= std::min(k, m); i++) { |
| const float f = |
| (choose(m, i) * choose(n, k - i)) / static_cast<float>(choose(m + n, k)); |
| aSq += a.fWeights[i] * a.fWeights[k - i] * f; |
| bSq += b.fWeights[i] * b.fWeights[k - i] * f; |
| } |
| result.fWeights[k] = aSq + bSq; |
| } |
| |
| return result; |
| } |
| |
| /** Returns a - b. */ |
| static ScalarBezCurve Sub(const ScalarBezCurve& a, const ScalarBezCurve& b) { |
| ScalarBezCurve result = a; |
| result.sub(b); |
| return result; |
| } |
| |
| /** Subtracts the other curve from this curve */ |
| void sub(const ScalarBezCurve& other) { |
| SkASSERT(other.fDegree == fDegree); |
| for (int k = 0; k <= fDegree; k++) { |
| fWeights[k] -= other.fWeights[k]; |
| } |
| } |
| |
| /** Subtracts a constant from this curve */ |
| void sub(float f) { |
| for (int k = 0; k <= fDegree; k++) { |
| fWeights[k] -= f; |
| } |
| } |
| |
| /** Returns the curve degree */ |
| int degree() const { return fDegree; } |
| |
| /** Returns the curve weights */ |
| const std::vector<float>& weights() const { return fWeights; } |
| |
| float operator[](size_t i) const { return fWeights[i]; } |
| float& operator[](size_t i) { return fWeights[i]; } |
| |
| private: |
| /** Recursive helper for ZeroSet */ |
| static void ZeroSetRec(const ScalarBezCurve& curve, |
| float tmin, |
| float tmax, |
| float tol, |
| std::vector<float>* result) { |
| float lenP = 0; |
| bool allPos = curve.fWeights[0] >= 0, allNeg = curve.fWeights[0] < 0; |
| for (int i = 1; i <= curve.fDegree; i++) { |
| lenP += std::abs(curve.fWeights[i] - curve.fWeights[i - 1]); |
| allPos &= curve.fWeights[i] >= 0; |
| allNeg &= curve.fWeights[i] < 0; |
| } |
| if (lenP <= tol) { |
| result->push_back((tmin + tmax) * 0.5); |
| return; |
| } else if (allPos || allNeg) { |
| // No zero crossings possible if the coefficients don't change sign (convex hull |
| // property) |
| return; |
| } else if (SkScalarNearlyZero(tmax - tmin)) { |
| return; |
| } else { |
| ScalarBezCurve left(curve.fDegree), right(curve.fDegree); |
| Split(curve, 0.5f, &left, &right); |
| |
| const float tmid = (tmin + tmax) * 0.5; |
| ZeroSetRec(left, tmin, tmid, tol, result); |
| ZeroSetRec(right, tmid, tmax, tol, result); |
| } |
| } |
| |
| int fDegree; |
| std::vector<float> fWeights; |
| }; |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| /** Helper class that measures per-verb path lengths. */ |
| class PathVerbMeasure { |
| public: |
| explicit PathVerbMeasure(const SkPath& path) : fPath(path), fIter(path, false) { nextVerb(); } |
| |
| SkScalar totalLength() const; |
| |
| SkScalar currentVerbLength() { return fMeas.getLength(); } |
| |
| void nextVerb(); |
| |
| private: |
| const SkPath& fPath; |
| SkPoint fFirstPointInContour; |
| SkPoint fPreviousPoint; |
| SkPath fCurrVerb; |
| SkPath::Iter fIter; |
| SkPathMeasure fMeas; |
| }; |
| |
| SkScalar PathVerbMeasure::totalLength() const { |
| SkPathMeasure meas(fPath, false); |
| return meas.getLength(); |
| } |
| |
| void PathVerbMeasure::nextVerb() { |
| SkPoint pts[4]; |
| SkPath::Verb verb = fIter.next(pts); |
| |
| while (verb == SkPath::kMove_Verb || verb == SkPath::kClose_Verb) { |
| if (verb == SkPath::kMove_Verb) { |
| fFirstPointInContour = pts[0]; |
| fPreviousPoint = fFirstPointInContour; |
| } |
| verb = fIter.next(pts); |
| } |
| |
| fCurrVerb.rewind(); |
| fCurrVerb.moveTo(fPreviousPoint); |
| switch (verb) { |
| case SkPath::kLine_Verb: |
| fCurrVerb.lineTo(pts[1]); |
| break; |
| case SkPath::kQuad_Verb: |
| fCurrVerb.quadTo(pts[1], pts[2]); |
| break; |
| case SkPath::kCubic_Verb: |
| fCurrVerb.cubicTo(pts[1], pts[2], pts[3]); |
| break; |
| case SkPath::kConic_Verb: |
| fCurrVerb.conicTo(pts[1], pts[2], fIter.conicWeight()); |
| break; |
| case SkPath::kDone_Verb: |
| break; |
| case SkPath::kClose_Verb: |
| case SkPath::kMove_Verb: |
| SkASSERT(false); |
| break; |
| } |
| |
| fCurrVerb.getLastPt(&fPreviousPoint); |
| fMeas.setPath(&fCurrVerb, false); |
| } |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| // Several debug-only visualization helpers |
| namespace viz { |
| std::unique_ptr<ScalarBezCurve> outerErr; |
| SkPath outerFirstApprox; |
| } // namespace viz |
| |
| /** |
| * Prototype variable-width path stroker. |
| * |
| * Takes as input a path to be stroked, and two distance functions (inside and outside). |
| * Produces a fill path with the stroked path geometry. |
| * |
| * The algorithms in use here are from: |
| * |
| * G. Elber, E. Cohen. "Error bounded variable distance offset operator for free form curves and |
| * surfaces." International Journal of Computational Geometry & Applications 1, no. 01 (1991) |
| * |
| * G. Elber. "Free form surface analysis using a hybrid of symbolic and numeric computation." |
| * PhD diss., Dept. of Computer Science, University of Utah, 1992. |
| */ |
| class SkVarWidthStroker { |
| public: |
| /** Metric to use for interpolation of distance function across path segments. */ |
| enum class LengthMetric { |
| /** Each path segment gets an equal interval of t in [0,1] */ |
| kNumSegments, |
| /** Each path segment gets t interval equal to its percent of the total path length */ |
| kPathLength, |
| }; |
| |
| /** |
| * Strokes the path with a fixed-width distance function. This produces a traditional stroked |
| * path. |
| */ |
| SkPath getFillPath(const SkPath& path, const SkPaint& paint) { |
| return getFillPath(path, paint, identityVarWidth(paint.getStrokeWidth()), |
| identityVarWidth(paint.getStrokeWidth())); |
| } |
| |
| /** |
| * Strokes the given path using the two given distance functions for inner and outer offsets. |
| */ |
| SkPath getFillPath(const SkPath& path, |
| const SkPaint& paint, |
| const ScalarBezCurve& varWidth, |
| const ScalarBezCurve& varWidthInner, |
| LengthMetric lengthMetric = LengthMetric::kNumSegments); |
| |
| private: |
| /** Helper struct referring to a single segment of an SkPath */ |
| struct PathSegment { |
| SkPath::Verb fVerb; |
| std::array<SkPoint, 4> fPoints; |
| }; |
| |
| struct OffsetSegments { |
| std::vector<PathSegment> fInner; |
| std::vector<PathSegment> fOuter; |
| }; |
| |
| /** Initialize stroker state */ |
| void initForPath(const SkPath& path, const SkPaint& paint); |
| |
| /** Strokes a path segment */ |
| OffsetSegments strokeSegment(const PathSegment& segment, |
| const ScalarBezCurve& varWidth, |
| const ScalarBezCurve& varWidthInner, |
| bool needsMove); |
| |
| /** |
| * Strokes the given segment using the given distance function. |
| * |
| * Returns a list of quad segments that approximate the offset curve. |
| * TODO: no reason this needs to return a vector of quads, can just append to the path |
| */ |
| std::vector<PathSegment> strokeSegment(const PathSegment& seg, |
| const ScalarBezCurve& distanceFunc) const; |
| |
| /** Adds an endcap to fOuter */ |
| enum class CapLocation { Start, End }; |
| void endcap(CapLocation loc); |
| |
| /** Adds a join between the two segments */ |
| void join(const SkPoint& common, |
| float innerRadius, |
| float outerRadius, |
| const OffsetSegments& prev, |
| const OffsetSegments& curr); |
| |
| /** Appends path in reverse to result */ |
| static void appendPathReversed(const SkPath& path, SkPath* result); |
| |
| /** Returns the segment unit normal and unit tangent if not nullptr */ |
| static SkPoint unitNormal(const PathSegment& seg, float t, SkPoint* tangentOut); |
| |
| /** Returns the degree of a segment curve */ |
| static int segmentDegree(const PathSegment& seg); |
| |
| /** Splits a path segment at t */ |
| static void splitSegment(const PathSegment& seg, float t, PathSegment* segA, PathSegment* segB); |
| |
| /** |
| * Returns a quadratic segment that approximates the given segment using the given distance |
| * function. |
| */ |
| static void approximateSegment(const PathSegment& seg, |
| const ScalarBezCurve& distFnc, |
| PathSegment* approxQuad); |
| |
| /** Returns a constant (deg 0) distance function for the given stroke width */ |
| static ScalarBezCurve identityVarWidth(float strokeWidth) { |
| return ScalarBezCurve(0, {strokeWidth / 2.0f}); |
| } |
| |
| float fRadius; |
| SkPaint::Cap fCap; |
| SkPaint::Join fJoin; |
| SkPath fInner, fOuter; |
| ScalarBezCurve fVarWidth, fVarWidthInner; |
| float fCurrT; |
| }; |
| |
| void SkVarWidthStroker::initForPath(const SkPath& path, const SkPaint& paint) { |
| fRadius = paint.getStrokeWidth() / 2; |
| fCap = paint.getStrokeCap(); |
| fJoin = paint.getStrokeJoin(); |
| fInner.rewind(); |
| fOuter.rewind(); |
| fCurrT = 0; |
| } |
| |
| SkPath SkVarWidthStroker::getFillPath(const SkPath& path, |
| const SkPaint& paint, |
| const ScalarBezCurve& varWidth, |
| const ScalarBezCurve& varWidthInner, |
| LengthMetric lengthMetric) { |
| const auto appendStrokes = [this](const OffsetSegments& strokes, bool needsMove) { |
| if (needsMove) { |
| fOuter.moveTo(strokes.fOuter.front().fPoints[0]); |
| fInner.moveTo(strokes.fInner.front().fPoints[0]); |
| } |
| |
| for (const PathSegment& seg : strokes.fOuter) { |
| fOuter.quadTo(seg.fPoints[1], seg.fPoints[2]); |
| } |
| |
| for (const PathSegment& seg : strokes.fInner) { |
| fInner.quadTo(seg.fPoints[1], seg.fPoints[2]); |
| } |
| }; |
| |
| initForPath(path, paint); |
| fVarWidth = varWidth; |
| fVarWidthInner = varWidthInner; |
| |
| // TODO: this assumes one contour: |
| PathVerbMeasure meas(path); |
| const float totalPathLength = lengthMetric == LengthMetric::kPathLength |
| ? meas.totalLength() |
| : (path.countVerbs() - 1); |
| |
| // Trace the inner and outer paths simultaneously. Inner will therefore be |
| // recorded in reverse from how we trace the outline. |
| SkPath::Iter it(path, false); |
| PathSegment segment, prevSegment; |
| OffsetSegments offsetSegs, prevOffsetSegs; |
| bool firstSegment = true, prevWasFirst = false; |
| |
| float lenTraveled = 0; |
| while ((segment.fVerb = it.next(&segment.fPoints[0])) != SkPath::kDone_Verb) { |
| const float verbLength = lengthMetric == LengthMetric::kPathLength |
| ? (meas.currentVerbLength() / totalPathLength) |
| : (1.0f / totalPathLength); |
| const float tmin = lenTraveled; |
| const float tmax = lenTraveled + verbLength; |
| |
| // Subset the distance function for the current interval. |
| ScalarBezCurve partVarWidth, partVarWidthInner; |
| fVarWidth.split(tmin, tmax, &partVarWidth); |
| fVarWidthInner.split(tmin, tmax, &partVarWidthInner); |
| partVarWidthInner = ScalarBezCurve::Mul(partVarWidthInner, -1); |
| |
| // Stroke the current segment |
| switch (segment.fVerb) { |
| case SkPath::kLine_Verb: |
| case SkPath::kQuad_Verb: |
| case SkPath::kCubic_Verb: |
| offsetSegs = strokeSegment(segment, partVarWidth, partVarWidthInner, firstSegment); |
| break; |
| case SkPath::kMove_Verb: |
| // Don't care about multiple contours currently |
| continue; |
| default: |
| SkDebugf("Unhandled path verb %d\n", segment.fVerb); |
| SkASSERT(false); |
| break; |
| } |
| |
| // Join to the previous segment |
| if (!firstSegment) { |
| // Append prev inner and outer strokes |
| appendStrokes(prevOffsetSegs, prevWasFirst); |
| |
| // Append the join |
| const float innerRadius = varWidthInner.eval(tmin); |
| const float outerRadius = varWidth.eval(tmin); |
| join(segment.fPoints[0], innerRadius, outerRadius, prevOffsetSegs, offsetSegs); |
| } |
| |
| std::swap(segment, prevSegment); |
| std::swap(offsetSegs, prevOffsetSegs); |
| prevWasFirst = firstSegment; |
| firstSegment = false; |
| lenTraveled += verbLength; |
| meas.nextVerb(); |
| } |
| |
| // Finish appending final offset segments |
| appendStrokes(prevOffsetSegs, prevWasFirst); |
| |
| // Open contour => endcap at the end |
| const bool isClosed = path.isLastContourClosed(); |
| if (isClosed) { |
| SkDebugf("Unhandled closed contour\n"); |
| SkASSERT(false); |
| } else { |
| endcap(CapLocation::End); |
| } |
| |
| // Walk inner path in reverse, appending to result |
| appendPathReversed(fInner, &fOuter); |
| endcap(CapLocation::Start); |
| |
| return fOuter; |
| } |
| |
| SkVarWidthStroker::OffsetSegments SkVarWidthStroker::strokeSegment( |
| const PathSegment& segment, |
| const ScalarBezCurve& varWidth, |
| const ScalarBezCurve& varWidthInner, |
| bool needsMove) { |
| viz::outerErr.reset(nullptr); |
| |
| std::vector<PathSegment> outer = strokeSegment(segment, varWidth); |
| std::vector<PathSegment> inner = strokeSegment(segment, varWidthInner); |
| return {inner, outer}; |
| } |
| |
| std::vector<SkVarWidthStroker::PathSegment> SkVarWidthStroker::strokeSegment( |
| const PathSegment& seg, const ScalarBezCurve& distanceFunc) const { |
| // Work item for the recursive splitting stack. |
| struct Item { |
| PathSegment fSeg; |
| ScalarBezCurve fDistFnc, fDistFncSqd; |
| ScalarBezCurve fSegX, fSegY; |
| |
| Item(const PathSegment& seg, |
| const ScalarBezCurve& distFnc, |
| const ScalarBezCurve& distFncSqd) |
| : fSeg(seg), fDistFnc(distFnc), fDistFncSqd(distFncSqd) { |
| const int segDegree = segmentDegree(seg); |
| fSegX = ScalarBezCurve(segDegree); |
| fSegY = ScalarBezCurve(segDegree); |
| for (int i = 0; i <= segDegree; i++) { |
| fSegX[i] = seg.fPoints[i].fX; |
| fSegY[i] = seg.fPoints[i].fY; |
| } |
| } |
| }; |
| |
| // Push the initial segment and distance function |
| std::stack<Item> stack; |
| stack.push(Item(seg, distanceFunc, ScalarBezCurve::Mul(distanceFunc, distanceFunc))); |
| |
| std::vector<PathSegment> result; |
| constexpr int kMaxIters = 5000; /** TODO: this is completely arbitrary */ |
| int iter = 0; |
| while (!stack.empty()) { |
| if (iter++ >= kMaxIters) break; |
| const Item item = stack.top(); |
| stack.pop(); |
| |
| const ScalarBezCurve& distFnc = item.fDistFnc; |
| ScalarBezCurve distFncSqd = item.fDistFncSqd; |
| const float kTol = std::abs(0.5f * distFnc.extremumWeight()); |
| |
| // Compute a quad that approximates stroke outline |
| PathSegment quadApprox; |
| approximateSegment(item.fSeg, distFnc, &quadApprox); |
| ScalarBezCurve quadApproxX(2), quadApproxY(2); |
| for (int i = 0; i < 3; i++) { |
| quadApproxX[i] = quadApprox.fPoints[i].fX; |
| quadApproxY[i] = quadApprox.fPoints[i].fY; |
| } |
| |
| // Compute control polygon for the delta(t) curve. First must elevate to a common degree. |
| const int deltaDegree = std::max(quadApproxX.degree(), item.fSegX.degree()); |
| ScalarBezCurve segX = item.fSegX, segY = item.fSegY; |
| segX.elevateDegree(deltaDegree); |
| segY.elevateDegree(deltaDegree); |
| quadApproxX.elevateDegree(deltaDegree); |
| quadApproxY.elevateDegree(deltaDegree); |
| |
| ScalarBezCurve deltaX = ScalarBezCurve::Sub(quadApproxX, segX); |
| ScalarBezCurve deltaY = ScalarBezCurve::Sub(quadApproxY, segY); |
| |
| // Compute psi(t) = delta_x(t)^2 + delta_y(t)^2. |
| ScalarBezCurve E = ScalarBezCurve::AddSquares(deltaX, deltaY); |
| |
| // Promote E and d(t)^2 to a common degree. |
| const int commonDeg = std::max(distFncSqd.degree(), E.degree()); |
| distFncSqd.elevateDegree(commonDeg); |
| E.elevateDegree(commonDeg); |
| |
| // Subtract dist squared curve from E, resulting in: |
| // eps(t) = delta_x(t)^2 + delta_y(t)^2 - d(t)^2 |
| E.sub(distFncSqd); |
| |
| // Purely for debugging/testing, save the first approximation and error function: |
| if (viz::outerErr == nullptr) { |
| using namespace viz; |
| outerErr = std::make_unique<ScalarBezCurve>(E); |
| outerFirstApprox.rewind(); |
| outerFirstApprox.moveTo(quadApprox.fPoints[0]); |
| outerFirstApprox.quadTo(quadApprox.fPoints[1], quadApprox.fPoints[2]); |
| } |
| |
| // Compute maxErr, which is just the max coefficient of eps (using convex hull property |
| // of bez curves) |
| float maxAbsErr = std::abs(E.extremumWeight()); |
| |
| if (maxAbsErr > kTol) { |
| PathSegment left, right; |
| splitSegment(item.fSeg, 0.5f, &left, &right); |
| |
| ScalarBezCurve distFncL, distFncR; |
| distFnc.split(0.5f, &distFncL, &distFncR); |
| |
| ScalarBezCurve distFncSqdL, distFncSqdR; |
| distFncSqd.split(0.5f, &distFncSqdL, &distFncSqdR); |
| |
| stack.push(Item(right, distFncR, distFncSqdR)); |
| stack.push(Item(left, distFncL, distFncSqdL)); |
| } else { |
| // Approximation is good enough. |
| quadApprox.fVerb = SkPath::kQuad_Verb; |
| result.push_back(quadApprox); |
| } |
| } |
| SkASSERT(!result.empty()); |
| return result; |
| } |
| |
| void SkVarWidthStroker::endcap(CapLocation loc) { |
| const auto buttCap = [this](CapLocation loc) { |
| if (loc == CapLocation::Start) { |
| // Back at the start of the path: just close the stroked outline |
| fOuter.close(); |
| } else { |
| // Inner last pt == first pt when appending in reverse |
| SkPoint innerLastPt; |
| fInner.getLastPt(&innerLastPt); |
| fOuter.lineTo(innerLastPt); |
| } |
| }; |
| |
| switch (fCap) { |
| case SkPaint::kButt_Cap: |
| buttCap(loc); |
| break; |
| default: |
| SkDebugf("Unhandled endcap %d\n", fCap); |
| buttCap(loc); |
| break; |
| } |
| } |
| |
| void SkVarWidthStroker::join(const SkPoint& common, |
| float innerRadius, |
| float outerRadius, |
| const OffsetSegments& prev, |
| const OffsetSegments& curr) { |
| const auto miterJoin = [this](const SkPoint& common, |
| float leftRadius, |
| float rightRadius, |
| const OffsetSegments& prev, |
| const OffsetSegments& curr) { |
| // With variable-width stroke you can actually have a situation where both sides |
| // need an "inner" or an "outer" join. So we call the two sides "left" and |
| // "right" and they can each independently get an inner or outer join. |
| const auto makeJoin = [this, &common, &prev, &curr](bool left, float radius) { |
| SkPath* path = left ? &fOuter : &fInner; |
| const auto& prevSegs = left ? prev.fOuter : prev.fInner; |
| const auto& currSegs = left ? curr.fOuter : curr.fInner; |
| SkASSERT(!prevSegs.empty()); |
| SkASSERT(!currSegs.empty()); |
| const SkPoint afterEndpt = currSegs.front().fPoints[0]; |
| SkPoint before = unitNormal(prevSegs.back(), 1, nullptr); |
| SkPoint after = unitNormal(currSegs.front(), 0, nullptr); |
| |
| // Don't create any join geometry if the normals are nearly identical. |
| const float cosTheta = before.dot(after); |
| if (!SkScalarNearlyZero(1 - cosTheta)) { |
| bool outerJoin; |
| if (left) { |
| outerJoin = isClockwise(before, after); |
| } else { |
| before = rotate180(before); |
| after = rotate180(after); |
| outerJoin = !isClockwise(before, after); |
| } |
| |
| if (outerJoin) { |
| // Before and after have the same origin and magnitude, so before+after is the |
| // diagonal of their rhombus. Origin of this vector is the midpoint of the miter |
| // line. |
| SkPoint miterVec = before + after; |
| |
| // Note the relationship (draw a right triangle with the miter line as its |
| // hypoteneuse): |
| // sin(theta/2) = strokeWidth / miterLength |
| // so miterLength = strokeWidth / sin(theta/2) |
| // where miterLength is the length of the miter from outer point to inner |
| // corner. miterVec's origin is the midpoint of the miter line, so we use |
| // strokeWidth/2. Sqrt is just an application of half-angle identities. |
| const float sinHalfTheta = sqrtf(0.5 * (1 + cosTheta)); |
| const float halfMiterLength = radius / sinHalfTheta; |
| // TODO: miter length limit |
| miterVec = setLength(miterVec, halfMiterLength); |
| |
| // Outer join: connect to the miter point, and then to t=0 of next segment. |
| path->lineTo(common + miterVec); |
| path->lineTo(afterEndpt); |
| } else { |
| // Connect to the miter midpoint (common path endpoint of the two segments), |
| // and then to t=0 of the next segment. This adds an interior "loop" |
| // of geometry that handles edge cases where segment lengths are shorter than |
| // the stroke width. |
| path->lineTo(common); |
| path->lineTo(afterEndpt); |
| } |
| } |
| }; |
| |
| makeJoin(true, leftRadius); |
| makeJoin(false, rightRadius); |
| }; |
| |
| switch (fJoin) { |
| case SkPaint::kMiter_Join: |
| miterJoin(common, innerRadius, outerRadius, prev, curr); |
| break; |
| default: |
| SkDebugf("Unhandled join %d\n", fJoin); |
| miterJoin(common, innerRadius, outerRadius, prev, curr); |
| break; |
| } |
| } |
| |
| void SkVarWidthStroker::appendPathReversed(const SkPath& path, SkPath* result) { |
| const int numVerbs = path.countVerbs(); |
| const int numPoints = path.countPoints(); |
| std::vector<uint8_t> verbs; |
| std::vector<SkPoint> points; |
| verbs.resize(numVerbs); |
| points.resize(numPoints); |
| path.getVerbs(verbs.data(), numVerbs); |
| path.getPoints(points.data(), numPoints); |
| |
| for (int i = numVerbs - 1, j = numPoints; i >= 0; i--) { |
| auto verb = static_cast<SkPath::Verb>(verbs[i]); |
| switch (verb) { |
| case SkPath::kLine_Verb: { |
| j -= 1; |
| SkASSERT(j >= 1); |
| result->lineTo(points[j - 1]); |
| break; |
| } |
| case SkPath::kQuad_Verb: { |
| j -= 1; |
| SkASSERT(j >= 2); |
| result->quadTo(points[j - 1], points[j - 2]); |
| j -= 1; |
| break; |
| } |
| case SkPath::kMove_Verb: |
| // Ignore |
| break; |
| default: |
| SkASSERT(false); |
| break; |
| } |
| } |
| } |
| |
| int SkVarWidthStroker::segmentDegree(const PathSegment& seg) { |
| static constexpr int lut[] = { |
| -1, // move, |
| 1, // line |
| 2, // quad |
| -1, // conic |
| 3, // cubic |
| -1 // done |
| }; |
| const int deg = lut[static_cast<uint8_t>(seg.fVerb)]; |
| SkASSERT(deg > 0); |
| return deg; |
| } |
| |
| void SkVarWidthStroker::splitSegment(const PathSegment& seg, |
| float t, |
| PathSegment* segA, |
| PathSegment* segB) { |
| // TODO: although general, this is a pretty slow way to do this |
| const int degree = segmentDegree(seg); |
| ScalarBezCurve x(degree), y(degree); |
| for (int i = 0; i <= degree; i++) { |
| x[i] = seg.fPoints[i].fX; |
| y[i] = seg.fPoints[i].fY; |
| } |
| |
| ScalarBezCurve leftX(degree), rightX(degree), leftY(degree), rightY(degree); |
| x.split(t, &leftX, &rightX); |
| y.split(t, &leftY, &rightY); |
| |
| segA->fVerb = segB->fVerb = seg.fVerb; |
| for (int i = 0; i <= degree; i++) { |
| segA->fPoints[i] = {leftX[i], leftY[i]}; |
| segB->fPoints[i] = {rightX[i], rightY[i]}; |
| } |
| } |
| |
| void SkVarWidthStroker::approximateSegment(const PathSegment& seg, |
| const ScalarBezCurve& distFnc, |
| PathSegment* approxQuad) { |
| // This is a simple control polygon transformation. |
| // From F. Yzerman. "Precise offsetting of quadratic Bezier curves". 2019. |
| // TODO: detect and handle more degenerate cases (e.g. linear) |
| // TODO: Tiller-Hanson works better in many cases but does not generalize well |
| SkPoint tangentStart, tangentEnd; |
| SkPoint offsetStart = unitNormal(seg, 0, &tangentStart); |
| SkPoint offsetEnd = unitNormal(seg, 1, &tangentEnd); |
| SkPoint offsetMid = offsetStart + offsetEnd; |
| |
| const float radiusStart = distFnc.eval(0); |
| const float radiusMid = distFnc.eval(0.5f); |
| const float radiusEnd = distFnc.eval(1); |
| |
| offsetStart = radiusStart == 0 ? SkPoint::Make(0, 0) : setLength(offsetStart, radiusStart); |
| offsetMid = radiusMid == 0 ? SkPoint::Make(0, 0) : setLength(offsetMid, radiusMid); |
| offsetEnd = radiusEnd == 0 ? SkPoint::Make(0, 0) : setLength(offsetEnd, radiusEnd); |
| |
| SkPoint start, mid, end; |
| switch (segmentDegree(seg)) { |
| case 1: |
| start = seg.fPoints[0]; |
| end = seg.fPoints[1]; |
| mid = (start + end) * 0.5f; |
| break; |
| case 2: |
| start = seg.fPoints[0]; |
| mid = seg.fPoints[1]; |
| end = seg.fPoints[2]; |
| break; |
| case 3: |
| start = seg.fPoints[0]; |
| mid = (seg.fPoints[1] + seg.fPoints[2]) * 0.5f; |
| end = seg.fPoints[3]; |
| break; |
| default: |
| SkDebugf("Unhandled degree for segment approximation"); |
| SkASSERT(false); |
| break; |
| } |
| |
| approxQuad->fPoints[0] = start + offsetStart; |
| approxQuad->fPoints[1] = mid + offsetMid; |
| approxQuad->fPoints[2] = end + offsetEnd; |
| } |
| |
| SkPoint SkVarWidthStroker::unitNormal(const PathSegment& seg, float t, SkPoint* tangentOut) { |
| switch (seg.fVerb) { |
| case SkPath::kLine_Verb: { |
| const SkPoint tangent = setLength(seg.fPoints[1] - seg.fPoints[0], 1); |
| const SkPoint normal = rotate90(tangent); |
| if (tangentOut) { |
| *tangentOut = tangent; |
| } |
| return normal; |
| } |
| case SkPath::kQuad_Verb: { |
| SkPoint tangent; |
| if (t == 0) { |
| tangent = seg.fPoints[1] - seg.fPoints[0]; |
| } else if (t == 1) { |
| tangent = seg.fPoints[2] - seg.fPoints[1]; |
| } else { |
| tangent = ((seg.fPoints[1] - seg.fPoints[0]) * (1 - t) + |
| (seg.fPoints[2] - seg.fPoints[1]) * t) * |
| 2; |
| } |
| if (!tangent.normalize()) { |
| SkDebugf("Failed to normalize quad tangent\n"); |
| SkASSERT(false); |
| } |
| if (tangentOut) { |
| *tangentOut = tangent; |
| } |
| return rotate90(tangent); |
| } |
| case SkPath::kCubic_Verb: { |
| SkPoint tangent; |
| SkEvalCubicAt(seg.fPoints.data(), t, nullptr, &tangent, nullptr); |
| if (!tangent.normalize()) { |
| SkDebugf("Failed to normalize cubic tangent\n"); |
| SkASSERT(false); |
| } |
| if (tangentOut) { |
| *tangentOut = tangent; |
| } |
| return rotate90(tangent); |
| } |
| default: |
| SkDebugf("Unhandled verb for unit normal %d\n", seg.fVerb); |
| SkASSERT(false); |
| return {}; |
| } |
| } |
| |
| } // namespace |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| class VariableWidthStroker : public Sample { |
| public: |
| VariableWidthStroker() |
| : fShowHidden(true) |
| , fShowSkeleton(true) |
| , fShowStrokePoints(false) |
| , fShowUI(false) |
| , fDifferentInnerFunc(false) |
| , fShowErrorCurve(false) { |
| resetToDefaults(); |
| |
| fPtsPaint.setAntiAlias(true); |
| fPtsPaint.setStrokeWidth(10); |
| fPtsPaint.setStrokeCap(SkPaint::kRound_Cap); |
| |
| fStrokePointsPaint.setAntiAlias(true); |
| fStrokePointsPaint.setStrokeWidth(5); |
| fStrokePointsPaint.setStrokeCap(SkPaint::kRound_Cap); |
| |
| fStrokePaint.setAntiAlias(true); |
| fStrokePaint.setStyle(SkPaint::kStroke_Style); |
| fStrokePaint.setColor(0x80FF0000); |
| |
| fNewFillPaint.setAntiAlias(true); |
| fNewFillPaint.setColor(0x8000FF00); |
| |
| fHiddenPaint.setAntiAlias(true); |
| fHiddenPaint.setStyle(SkPaint::kStroke_Style); |
| fHiddenPaint.setColor(0xFF0000FF); |
| |
| fSkeletonPaint.setAntiAlias(true); |
| fSkeletonPaint.setStyle(SkPaint::kStroke_Style); |
| fSkeletonPaint.setColor(SK_ColorRED); |
| } |
| |
| private: |
| /** Selectable menu item for choosing distance functions */ |
| struct DistFncMenuItem { |
| std::string fName; |
| int fDegree; |
| bool fSelected; |
| std::vector<float> fWeights; |
| |
| DistFncMenuItem(const std::string& name, int degree, bool selected) { |
| fName = name; |
| fDegree = degree; |
| fSelected = selected; |
| fWeights.resize(degree + 1, 1.0f); |
| } |
| }; |
| |
| SkString name() override { return SkString("VariableWidthStroker"); } |
| |
| void onSizeChange() override { |
| fWinSize = SkSize::Make(this->width(), this->height()); |
| INHERITED::onSizeChange(); |
| } |
| |
| bool onChar(SkUnichar uni) override { |
| switch (uni) { |
| case '0': |
| this->toggle(fShowUI); |
| return true; |
| case '1': |
| this->toggle(fShowSkeleton); |
| return true; |
| case '2': |
| this->toggle(fShowHidden); |
| return true; |
| case '3': |
| this->toggle(fShowStrokePoints); |
| return true; |
| case '4': |
| this->toggle(fShowErrorCurve); |
| return true; |
| case '5': |
| this->toggle(fLengthMetric); |
| return true; |
| case 'x': |
| resetToDefaults(); |
| return true; |
| case '-': |
| fWidth -= 5; |
| return true; |
| case '=': |
| fWidth += 5; |
| return true; |
| default: |
| break; |
| } |
| return false; |
| } |
| |
| void toggle(bool& value) { value = !value; } |
| void toggle(SkVarWidthStroker::LengthMetric& value) { |
| value = value == SkVarWidthStroker::LengthMetric::kPathLength |
| ? SkVarWidthStroker::LengthMetric::kNumSegments |
| : SkVarWidthStroker::LengthMetric::kPathLength; |
| } |
| |
| void resetToDefaults() { |
| fPathPts[0] = {300, 400}; |
| fPathPts[1] = {500, 400}; |
| fPathPts[2] = {700, 400}; |
| fPathPts[3] = {900, 400}; |
| fPathPts[4] = {1100, 400}; |
| |
| fWidth = 175; |
| |
| fLengthMetric = SkVarWidthStroker::LengthMetric::kPathLength; |
| fDistFncs = fDefaultsDistFncs; |
| fDistFncsInner = fDefaultsDistFncs; |
| } |
| |
| void makePath(SkPath* path) { |
| path->moveTo(fPathPts[0]); |
| path->quadTo(fPathPts[1], fPathPts[2]); |
| path->quadTo(fPathPts[3], fPathPts[4]); |
| } |
| |
| static ScalarBezCurve makeDistFnc(const std::vector<DistFncMenuItem>& fncs, float strokeWidth) { |
| const float radius = strokeWidth / 2; |
| for (const auto& df : fncs) { |
| if (df.fSelected) { |
| return ScalarBezCurve::Mul(ScalarBezCurve(df.fDegree, df.fWeights), radius); |
| } |
| } |
| SkASSERT(false); |
| return ScalarBezCurve(0, {radius}); |
| } |
| |
| void onDrawContent(SkCanvas* canvas) override { |
| canvas->drawColor(0xFFEEEEEE); |
| |
| SkPath path; |
| this->makePath(&path); |
| |
| fStrokePaint.setStrokeWidth(fWidth); |
| |
| // Elber-Cohen stroker result |
| ScalarBezCurve distFnc = makeDistFnc(fDistFncs, fWidth); |
| ScalarBezCurve distFncInner = |
| fDifferentInnerFunc ? makeDistFnc(fDistFncsInner, fWidth) : distFnc; |
| SkVarWidthStroker stroker; |
| SkPath fillPath = |
| stroker.getFillPath(path, fStrokePaint, distFnc, distFncInner, fLengthMetric); |
| fillPath.setFillType(SkPathFillType::kWinding); |
| canvas->drawPath(fillPath, fNewFillPaint); |
| |
| if (fShowHidden) { |
| canvas->drawPath(fillPath, fHiddenPaint); |
| } |
| |
| if (fShowSkeleton) { |
| canvas->drawPath(path, fSkeletonPaint); |
| canvas->drawPoints(SkCanvas::kPoints_PointMode, fPathPts.size(), fPathPts.data(), |
| fPtsPaint); |
| } |
| |
| if (fShowStrokePoints) { |
| drawStrokePoints(canvas, fillPath); |
| } |
| |
| if (fShowUI) { |
| drawUI(); |
| } |
| |
| if (fShowErrorCurve && viz::outerErr != nullptr) { |
| SkPaint firstApproxPaint; |
| firstApproxPaint.setStrokeWidth(4); |
| firstApproxPaint.setStyle(SkPaint::kStroke_Style); |
| firstApproxPaint.setColor(SK_ColorRED); |
| canvas->drawPath(viz::outerFirstApprox, firstApproxPaint); |
| drawErrorCurve(canvas, *viz::outerErr); |
| } |
| } |
| |
| Sample::Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override { |
| const SkScalar tol = 4; |
| const SkRect r = SkRect::MakeXYWH(x - tol, y - tol, tol * 2, tol * 2); |
| for (size_t i = 0; i < fPathPts.size(); ++i) { |
| if (r.intersects(SkRect::MakeXYWH(fPathPts[i].fX, fPathPts[i].fY, 1, 1))) { |
| return new Click([this, i](Click* c) { |
| fPathPts[i] = c->fCurr; |
| return true; |
| }); |
| } |
| } |
| return nullptr; |
| } |
| |
| void drawStrokePoints(SkCanvas* canvas, const SkPath& fillPath) { |
| SkPath::Iter it(fillPath, false); |
| SkPoint points[4]; |
| SkPath::Verb verb; |
| std::vector<SkPoint> pointsVec, ctrlPts; |
| while ((verb = it.next(&points[0])) != SkPath::kDone_Verb) { |
| switch (verb) { |
| case SkPath::kLine_Verb: |
| pointsVec.push_back(points[1]); |
| break; |
| case SkPath::kQuad_Verb: |
| ctrlPts.push_back(points[1]); |
| pointsVec.push_back(points[2]); |
| break; |
| case SkPath::kMove_Verb: |
| pointsVec.push_back(points[0]); |
| break; |
| case SkPath::kClose_Verb: |
| break; |
| default: |
| SkDebugf("Unhandled path verb %d for stroke points\n", verb); |
| SkASSERT(false); |
| break; |
| } |
| } |
| |
| canvas->drawPoints(SkCanvas::kPoints_PointMode, pointsVec.size(), pointsVec.data(), |
| fStrokePointsPaint); |
| fStrokePointsPaint.setColor(SK_ColorBLUE); |
| fStrokePointsPaint.setStrokeWidth(3); |
| canvas->drawPoints(SkCanvas::kPoints_PointMode, ctrlPts.size(), ctrlPts.data(), |
| fStrokePointsPaint); |
| fStrokePointsPaint.setColor(SK_ColorBLACK); |
| fStrokePointsPaint.setStrokeWidth(5); |
| } |
| |
| void drawErrorCurve(SkCanvas* canvas, const ScalarBezCurve& E) { |
| const float winW = fWinSize.width() * 0.75f, winH = fWinSize.height() * 0.25f; |
| const float padding = 25; |
| const SkRect box = SkRect::MakeXYWH(padding, fWinSize.height() - winH - padding, |
| winW - 2 * padding, winH); |
| constexpr int nsegs = 100; |
| constexpr float dt = 1.0f / nsegs; |
| constexpr float dx = 10.0f; |
| const int deg = E.degree(); |
| SkPath path; |
| for (int i = 0; i < nsegs; i++) { |
| const float tmin = i * dt, tmax = (i + 1) * dt; |
| ScalarBezCurve left(deg), right(deg); |
| E.split(tmax, &left, &right); |
| const float tRel = tmin / tmax; |
| ScalarBezCurve rl(deg), rr(deg); |
| left.split(tRel, &rl, &rr); |
| |
| const float x = i * dx; |
| if (i == 0) { |
| path.moveTo(x, -rr[0]); |
| } |
| path.lineTo(x + dx, -rr[deg]); |
| } |
| |
| SkPaint paint; |
| paint.setStyle(SkPaint::kStroke_Style); |
| paint.setAntiAlias(true); |
| paint.setStrokeWidth(0); |
| paint.setColor(SK_ColorRED); |
| const SkRect pathBounds = path.computeTightBounds(); |
| constexpr float yAxisMax = 8000; |
| const float sx = box.width() / pathBounds.width(); |
| const float sy = box.height() / (2 * yAxisMax); |
| canvas->save(); |
| canvas->translate(box.left(), box.top() + box.height() / 2); |
| canvas->scale(sx, sy); |
| canvas->drawPath(path, paint); |
| |
| SkPath axes; |
| axes.moveTo(0, 0); |
| axes.lineTo(pathBounds.width(), 0); |
| axes.moveTo(0, -yAxisMax); |
| axes.lineTo(0, yAxisMax); |
| paint.setColor(SK_ColorBLACK); |
| paint.setAntiAlias(false); |
| canvas->drawPath(axes, paint); |
| |
| canvas->restore(); |
| } |
| |
| void drawUI() { |
| static constexpr auto kUIOpacity = 0.35f; |
| static constexpr float kUIWidth = 200.0f, kUIHeight = 400.0f; |
| ImGui::SetNextWindowBgAlpha(kUIOpacity); |
| if (ImGui::Begin("E-C Controls", nullptr, |
| ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize | |
| ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoSavedSettings | |
| ImGuiWindowFlags_NoFocusOnAppearing | ImGuiWindowFlags_NoNav)) { |
| const SkRect uiArea = SkRect::MakeXYWH(10, 10, kUIWidth, kUIHeight); |
| ImGui::SetWindowPos(ImVec2(uiArea.x(), uiArea.y())); |
| ImGui::SetWindowSize(ImVec2(uiArea.width(), uiArea.height())); |
| |
| const auto drawControls = [](std::vector<DistFncMenuItem>& distFncs, |
| const std::string& menuPfx, |
| const std::string& ptPfx) { |
| std::string degreeMenuLabel = menuPfx + ": "; |
| for (const auto& df : distFncs) { |
| if (df.fSelected) { |
| degreeMenuLabel += df.fName; |
| break; |
| } |
| } |
| if (ImGui::BeginMenu(degreeMenuLabel.c_str())) { |
| for (size_t i = 0; i < distFncs.size(); i++) { |
| if (ImGui::MenuItem(distFncs[i].fName.c_str(), nullptr, |
| distFncs[i].fSelected)) { |
| for (size_t j = 0; j < distFncs.size(); j++) { |
| distFncs[j].fSelected = j == i; |
| } |
| } |
| } |
| ImGui::EndMenu(); |
| } |
| |
| for (auto& df : distFncs) { |
| if (df.fSelected) { |
| for (int i = 0; i <= df.fDegree; i++) { |
| const std::string label = ptPfx + std::to_string(i); |
| ImGui::SliderFloat(label.c_str(), &(df.fWeights[i]), 0, 1); |
| } |
| } |
| } |
| }; |
| |
| const std::array<std::pair<std::string, SkVarWidthStroker::LengthMetric>, 2> metrics = { |
| std::make_pair("% path length", SkVarWidthStroker::LengthMetric::kPathLength), |
| std::make_pair("% segment count", |
| SkVarWidthStroker::LengthMetric::kNumSegments), |
| }; |
| if (ImGui::BeginMenu("Interpolation metric:")) { |
| for (const auto& metric : metrics) { |
| if (ImGui::MenuItem(metric.first.c_str(), nullptr, |
| fLengthMetric == metric.second)) { |
| fLengthMetric = metric.second; |
| } |
| } |
| ImGui::EndMenu(); |
| } |
| |
| drawControls(fDistFncs, "Degree", "P"); |
| |
| if (ImGui::CollapsingHeader("Inner stroke", true)) { |
| fDifferentInnerFunc = true; |
| drawControls(fDistFncsInner, "Degree (inner)", "Q"); |
| } else { |
| fDifferentInnerFunc = false; |
| } |
| } |
| ImGui::End(); |
| } |
| |
| bool fShowHidden, fShowSkeleton, fShowStrokePoints, fShowUI, fDifferentInnerFunc, |
| fShowErrorCurve; |
| float fWidth = 175; |
| SkPaint fPtsPaint, fStrokePaint, fNewFillPaint, fHiddenPaint, fSkeletonPaint, |
| fStrokePointsPaint; |
| static constexpr int kNPts = 5; |
| std::array<SkPoint, kNPts> fPathPts; |
| SkSize fWinSize; |
| SkVarWidthStroker::LengthMetric fLengthMetric; |
| const std::vector<DistFncMenuItem> fDefaultsDistFncs = { |
| DistFncMenuItem("Linear", 1, true), DistFncMenuItem("Quadratic", 2, false), |
| DistFncMenuItem("Cubic", 3, false), DistFncMenuItem("One Louder (11)", 11, false), |
| DistFncMenuItem("30?!", 30, false)}; |
| std::vector<DistFncMenuItem> fDistFncs = fDefaultsDistFncs; |
| std::vector<DistFncMenuItem> fDistFncsInner = fDefaultsDistFncs; |
| |
| using INHERITED = Sample; |
| }; |
| |
| DEF_SAMPLE(return new VariableWidthStroker;) |