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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.
- */
- #include "include/core/SkPaint.h"
- #include "src/shaders/gradients/Sk4fGradientBase.h"
- #include <functional>
- namespace {
- Sk4f pack_color(const SkColor4f& c4f, bool premul, const Sk4f& component_scale) {
- Sk4f pm4f = premul
- ? Sk4f::Load(c4f.premul().vec())
- : Sk4f::Load(c4f.vec());
- if (premul) {
- // If the stops are premul, we clamp them to gamut now.
- // If the stops are unpremul, the colors will eventually go through Sk4f_toL32(),
- // which ends up clamping to gamut then.
- pm4f = Sk4f::Max(0, Sk4f::Min(pm4f, pm4f[3]));
- }
- return pm4f * component_scale;
- }
- class IntervalIterator {
- public:
- IntervalIterator(const SkGradientShaderBase& shader, bool reverse)
- : fShader(shader)
- , fFirstPos(reverse ? SK_Scalar1 : 0)
- , fBegin(reverse ? shader.fColorCount - 1 : 0)
- , fAdvance(reverse ? -1 : 1) {
- SkASSERT(shader.fColorCount > 0);
- }
- void iterate(const SkColor4f* colors,
- std::function<void(const SkColor4f&, const SkColor4f&,
- SkScalar, SkScalar)> func) const {
- if (!fShader.fOrigPos) {
- this->iterateImplicitPos(colors, func);
- return;
- }
- const int end = fBegin + fAdvance * (fShader.fColorCount - 1);
- int prev = fBegin;
- SkScalar prevPos = fFirstPos;
- do {
- const int curr = prev + fAdvance;
- SkASSERT(curr >= 0 && curr < fShader.fColorCount);
- const SkScalar currPos = fShader.fOrigPos[curr];
- if (currPos != prevPos) {
- SkASSERT((currPos - prevPos > 0) == (fAdvance > 0));
- func(colors[prev], colors[curr], prevPos, currPos);
- }
- prev = curr;
- prevPos = currPos;
- } while (prev != end);
- }
- private:
- void iterateImplicitPos(const SkColor4f* colors,
- std::function<void(const SkColor4f&, const SkColor4f&,
- SkScalar, SkScalar)> func) const {
- // When clients don't provide explicit color stop positions (fPos == nullptr),
- // the color stops are distributed evenly across the unit interval
- // (implicit positioning).
- const SkScalar dt = fAdvance * SK_Scalar1 / (fShader.fColorCount - 1);
- const int end = fBegin + fAdvance * (fShader.fColorCount - 2);
- int prev = fBegin;
- SkScalar prevPos = fFirstPos;
- while (prev != end) {
- const int curr = prev + fAdvance;
- SkASSERT(curr >= 0 && curr < fShader.fColorCount);
- const SkScalar currPos = prevPos + dt;
- func(colors[prev], colors[curr], prevPos, currPos);
- prev = curr;
- prevPos = currPos;
- }
- // emit the last interval with a pinned end position, to avoid precision issues
- func(colors[prev], colors[prev + fAdvance], prevPos, 1 - fFirstPos);
- }
- const SkGradientShaderBase& fShader;
- const SkScalar fFirstPos;
- const int fBegin;
- const int fAdvance;
- };
- void addMirrorIntervals(const SkGradientShaderBase& shader,
- const SkColor4f* colors,
- const Sk4f& componentScale,
- bool premulColors, bool reverse,
- Sk4fGradientIntervalBuffer::BufferType* buffer) {
- const IntervalIterator iter(shader, reverse);
- iter.iterate(colors, [&] (const SkColor4f& c0, const SkColor4f& c1, SkScalar t0, SkScalar t1) {
- SkASSERT(buffer->empty() || buffer->back().fT1 == 2 - t0);
- const auto mirror_t0 = 2 - t0;
- const auto mirror_t1 = 2 - t1;
- // mirror_p1 & mirror_p1 may collapse for very small values - recheck to avoid
- // triggering Interval asserts.
- if (mirror_t0 != mirror_t1) {
- buffer->emplace_back(pack_color(c0, premulColors, componentScale), mirror_t0,
- pack_color(c1, premulColors, componentScale), mirror_t1);
- }
- });
- }
- } // anonymous namespace
- Sk4fGradientInterval::Sk4fGradientInterval(const Sk4f& c0, SkScalar t0,
- const Sk4f& c1, SkScalar t1)
- : fT0(t0)
- , fT1(t1) {
- SkASSERT(t0 != t1);
- // Either p0 or p1 can be (-)inf for synthetic clamp edge intervals.
- SkASSERT(SkScalarIsFinite(t0) || SkScalarIsFinite(t1));
- const auto dt = t1 - t0;
- // Clamp edge intervals are always zero-ramp.
- SkASSERT(SkScalarIsFinite(dt) || (c0 == c1).allTrue());
- SkASSERT(SkScalarIsFinite(t0) || (c0 == c1).allTrue());
- const Sk4f dc = SkScalarIsFinite(dt) ? (c1 - c0) / dt : 0;
- const Sk4f bias = c0 - (SkScalarIsFinite(t0) ? t0 * dc : 0);
- bias.store(fCb.vec());
- dc.store(fCg.vec());
- }
- void Sk4fGradientIntervalBuffer::init(const SkGradientShaderBase& shader, SkColorSpace* dstCS,
- SkTileMode tileMode, bool premulColors,
- SkScalar alpha, bool reverse) {
- // The main job here is to build a specialized interval list: a different
- // representation of the color stops data, optimized for efficient scan line
- // access during shading.
- //
- // [{P0,C0} , {P1,C1}) [{P1,C2} , {P2,c3}) ... [{Pn,C2n} , {Pn+1,C2n+1})
- //
- // The list may be inverted when requested (such that e.g. points are sorted
- // in increasing x order when dx < 0).
- //
- // Note: the current representation duplicates pos data; we could refactor to
- // avoid this if interval storage size becomes a concern.
- //
- // Aside from reordering, we also perform two more pre-processing steps at
- // this stage:
- //
- // 1) scale the color components depending on paint alpha and the requested
- // interpolation space (note: the interval color storage is SkPMColor4f, but
- // that doesn't necessarily mean the colors are premultiplied; that
- // property is tracked in fColorsArePremul)
- //
- // 2) inject synthetic intervals to support tiling.
- //
- // * for kRepeat, no extra intervals are needed - the iterator just
- // wraps around at the end:
- //
- // ->[P0,P1)->..[Pn-1,Pn)->
- //
- // * for kClamp, we add two "infinite" intervals before/after:
- //
- // [-/+inf , P0)->[P0 , P1)->..[Pn-1 , Pn)->[Pn , +/-inf)
- //
- // (the iterator should never run off the end in this mode)
- //
- // * for kMirror, we extend the range to [0..2] and add a flipped
- // interval series - then the iterator operates just as in the
- // kRepeat case:
- //
- // ->[P0,P1)->..[Pn-1,Pn)->[2 - Pn,2 - Pn-1)->..[2 - P1,2 - P0)->
- //
- // TODO: investigate collapsing intervals << 1px.
- const auto count = shader.fColorCount;
- SkASSERT(count > 0);
- fIntervals.reset();
- const Sk4f componentScale = premulColors
- ? Sk4f(alpha)
- : Sk4f(1.0f, 1.0f, 1.0f, alpha);
- const int first_index = reverse ? count - 1 : 0;
- const int last_index = count - 1 - first_index;
- const SkScalar first_pos = reverse ? SK_Scalar1 : 0;
- const SkScalar last_pos = SK_Scalar1 - first_pos;
- // Transform all of the colors to destination color space
- SkColor4fXformer xformedColors(shader.fOrigColors4f, count, shader.fColorSpace.get(), dstCS);
- if (tileMode == SkTileMode::kClamp) {
- // synthetic edge interval: -/+inf .. P0
- const Sk4f clamp_color = pack_color(xformedColors.fColors[first_index],
- premulColors, componentScale);
- const SkScalar clamp_pos = reverse ? SK_ScalarInfinity : SK_ScalarNegativeInfinity;
- fIntervals.emplace_back(clamp_color, clamp_pos,
- clamp_color, first_pos);
- } else if (tileMode == SkTileMode::kMirror && reverse) {
- // synthetic mirror intervals injected before main intervals: (2 .. 1]
- addMirrorIntervals(shader, xformedColors.fColors, componentScale, premulColors, false,
- &fIntervals);
- }
- const IntervalIterator iter(shader, reverse);
- iter.iterate(xformedColors.fColors,
- [&] (const SkColor4f& c0, const SkColor4f& c1, SkScalar t0, SkScalar t1) {
- SkASSERT(fIntervals.empty() || fIntervals.back().fT1 == t0);
- fIntervals.emplace_back(pack_color(c0, premulColors, componentScale), t0,
- pack_color(c1, premulColors, componentScale), t1);
- });
- if (tileMode == SkTileMode::kClamp) {
- // synthetic edge interval: Pn .. +/-inf
- const Sk4f clamp_color = pack_color(xformedColors.fColors[last_index],
- premulColors, componentScale);
- const SkScalar clamp_pos = reverse ? SK_ScalarNegativeInfinity : SK_ScalarInfinity;
- fIntervals.emplace_back(clamp_color, last_pos,
- clamp_color, clamp_pos);
- } else if (tileMode == SkTileMode::kMirror && !reverse) {
- // synthetic mirror intervals injected after main intervals: [1 .. 2)
- addMirrorIntervals(shader, xformedColors.fColors, componentScale, premulColors, true,
- &fIntervals);
- }
- }
- const Sk4fGradientInterval* Sk4fGradientIntervalBuffer::find(SkScalar t) const {
- // Binary search.
- const auto* i0 = fIntervals.begin();
- const auto* i1 = fIntervals.end() - 1;
- while (i0 != i1) {
- SkASSERT(i0 < i1);
- SkASSERT(t >= i0->fT0 && t <= i1->fT1);
- const auto* i = i0 + ((i1 - i0) >> 1);
- if (t > i->fT1) {
- i0 = i + 1;
- } else {
- i1 = i;
- }
- }
- SkASSERT(i0->contains(t));
- return i0;
- }
- const Sk4fGradientInterval* Sk4fGradientIntervalBuffer::findNext(
- SkScalar t, const Sk4fGradientInterval* prev, bool increasing) const {
- SkASSERT(!prev->contains(t));
- SkASSERT(prev >= fIntervals.begin() && prev < fIntervals.end());
- SkASSERT(t >= fIntervals.front().fT0 && t <= fIntervals.back().fT1);
- const auto* i = prev;
- // Use the |increasing| signal to figure which direction we should search for
- // the next interval, then perform a linear search.
- if (increasing) {
- do {
- i += 1;
- if (i >= fIntervals.end()) {
- i = fIntervals.begin();
- }
- } while (!i->contains(t));
- } else {
- do {
- i -= 1;
- if (i < fIntervals.begin()) {
- i = fIntervals.end() - 1;
- }
- } while (!i->contains(t));
- }
- return i;
- }
- SkGradientShaderBase::
- GradientShaderBase4fContext::GradientShaderBase4fContext(const SkGradientShaderBase& shader,
- const ContextRec& rec)
- : INHERITED(shader, rec)
- , fFlags(this->INHERITED::getFlags())
- , fDither(rec.fPaint->isDither())
- {
- const SkMatrix& inverse = this->getTotalInverse();
- fDstToPos.setConcat(shader.fPtsToUnit, inverse);
- SkASSERT(!fDstToPos.hasPerspective());
- fDstToPosProc = SkMatrixPriv::GetMapXYProc(fDstToPos);
- if (shader.fColorsAreOpaque && this->getPaintAlpha() == SK_AlphaOPAQUE) {
- fFlags |= kOpaqueAlpha_Flag;
- }
- fColorsArePremul =
- (shader.fGradFlags & SkGradientShader::kInterpolateColorsInPremul_Flag)
- || shader.fColorsAreOpaque;
- }
- bool SkGradientShaderBase::
- GradientShaderBase4fContext::isValid() const {
- return fDstToPos.isFinite();
- }
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