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Unified Diff: src/effects/gradients/Sk4fGradientBase.cpp

Issue 1753853002: 4f gradient interval builder cleanup (Closed) Base URL: https://chromium.googlesource.com/skia.git@master
Patch Set: review commetns Created 4 years, 10 months ago
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Index: src/effects/gradients/Sk4fGradientBase.cpp
diff --git a/src/effects/gradients/Sk4fGradientBase.cpp b/src/effects/gradients/Sk4fGradientBase.cpp
index 442916638bc7642d1f9110c30b70abc28ace0a86..b3bc24658b7c5a6ed5bcab6c2e2f71694dbefe19 100644
--- a/src/effects/gradients/Sk4fGradientBase.cpp
+++ b/src/effects/gradients/Sk4fGradientBase.cpp
@@ -25,6 +25,83 @@ bool in_range(SkScalar x, SkScalar k1, SkScalar k2) {
: (x >= k2 && x < k1);
}
+class IntervalBuilder {
+public:
+ IntervalBuilder(const SkColor* colors, const SkScalar* pos, int count, bool reverse)
+ : fColors(colors)
+ , fPos(pos)
+ , fCount(count)
+ , fFirstPos(reverse ? SK_Scalar1 : 0)
+ , fBegin(reverse ? count - 1 : 0)
+ , fAdvance(reverse ? -1 : 1) {
+ SkASSERT(colors);
+ SkASSERT(count > 1);
+ }
+
+ template<typename F>
+ void build(F func) const {
+ if (!fPos) {
+ this->buildImplicitPos(func);
+ return;
+ }
+
+ const int end = fBegin + fAdvance * (fCount - 1);
+ const SkScalar lastPos = 1 - fFirstPos;
+ int prev = fBegin;
+ SkScalar prevPos = fFirstPos;
+
+ do {
+ const int curr = prev + fAdvance;
+ SkASSERT(curr >= 0 && curr < fCount);
+
+ // TODO: this sanitization should be done in SkGradientShaderBase
+ const SkScalar currPos = (fAdvance > 0)
+ ? SkTPin(fPos[curr], prevPos, lastPos)
+ : SkTPin(fPos[curr], lastPos, prevPos);
+
+ if (currPos != prevPos) {
+ SkASSERT((currPos - prevPos > 0) == (fAdvance > 0));
+ func(fColors[prev], fColors[curr], prevPos, currPos);
+ }
+
+ prev = curr;
+ prevPos = currPos;
+ } while (prev != end);
+ }
+
+private:
+ template<typename F>
+ void buildImplicitPos(F 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 / (fCount - 1);
+ const int end = fBegin + fAdvance * (fCount - 2);
+ int prev = fBegin;
+ SkScalar prevPos = fFirstPos;
+
+ while (prev != end) {
+ const int curr = prev + fAdvance;
+ SkASSERT(curr >= 0 && curr < fCount);
+
+ const SkScalar currPos = prevPos + dt;
+ func(fColors[prev], fColors[curr], prevPos, currPos);
+ prev = curr;
+ prevPos = currPos;
+ }
+
+ // emit the last interval with a pinned end position, to avoid precision issues
+ func(fColors[prev], fColors[prev + fAdvance], prevPos, 1 - fFirstPos);
+ }
+
+ const SkColor* fColors;
+ const SkScalar* fPos;
+ const int fCount;
+ const SkScalar fFirstPos;
+ const int fBegin;
+ const int fAdvance;
+};
+
} // anonymous namespace
SkGradientShaderBase::GradientShaderBase4fContext::
@@ -134,69 +211,38 @@ GradientShaderBase4fContext::GradientShaderBase4fContext(const SkGradientShaderB
SkASSERT(shader.fColorCount > 1);
SkASSERT(shader.fOrigColors);
- int direction = 1;
- int first_index = 0;
- int last_index = shader.fColorCount - 1;
- SkScalar first_pos = 0;
- SkScalar last_pos = 1;
const bool dx_is_pos = fDstToPos.getScaleX() >= 0;
- if (!dx_is_pos) {
- direction = -direction;
- SkTSwap(first_index, last_index);
- SkTSwap(first_pos, last_pos);
- }
+ const int first_index = dx_is_pos ? 0 : shader.fColorCount - 1;
+ const int last_index = shader.fColorCount - 1 - first_index;
+ const SkScalar first_pos = dx_is_pos ? 0 : SK_Scalar1;
+ const SkScalar last_pos = 1 - first_pos;
if (shader.fTileMode == SkShader::kClamp_TileMode) {
- // synthetic edge interval: -/+inf .. P0)
+ // synthetic edge interval: -/+inf .. P0
const SkPMColor clamp_color = pack_color(shader.fOrigColors[first_index],
fColorsArePremul);
const SkScalar clamp_pos = dx_is_pos ? SK_ScalarMin : SK_ScalarMax;
fIntervals.emplace_back(clamp_color, clamp_pos,
clamp_color, first_pos,
componentScale);
+ } else if (shader.fTileMode == SkShader::kMirror_TileMode && !dx_is_pos) {
+ // synthetic mirror intervals injected before main intervals: (2 .. 1]
+ addMirrorIntervals(shader, componentScale, dx_is_pos);
}
- int prev = first_index;
- int curr = prev + direction;
- SkScalar prev_pos = first_pos;
- if (shader.fOrigPos) {
- // explicit positions
- do {
- // TODO: this sanitization should be done in SkGradientShaderBase
- const SkScalar curr_pos = (dx_is_pos)
- ? SkTPin(shader.fOrigPos[curr], prev_pos, last_pos)
- : SkTPin(shader.fOrigPos[curr], last_pos, prev_pos);
- if (curr_pos != prev_pos) {
- fIntervals.emplace_back(
- pack_color(shader.fOrigColors[prev], fColorsArePremul),
- prev_pos,
- pack_color(shader.fOrigColors[curr], fColorsArePremul),
- curr_pos,
- componentScale);
- }
- prev = curr;
- prev_pos = curr_pos;
- curr += direction;
- } while (prev != last_index);
- } else {
- // implicit positions
- const SkScalar dt = direction * SK_Scalar1 / (shader.fColorCount - 1);
- do {
- const SkScalar curr_pos = prev_pos + dt;
- fIntervals.emplace_back(
- pack_color(shader.fOrigColors[prev], fColorsArePremul),
- prev_pos,
- pack_color(shader.fOrigColors[curr], fColorsArePremul),
- curr_pos,
- componentScale);
+ const IntervalBuilder builder(shader.fOrigColors,
+ shader.fOrigPos,
+ shader.fColorCount,
+ !dx_is_pos);
+ builder.build([this, &componentScale] (SkColor c0, SkColor c1, SkScalar p0, SkScalar p1) {
+ SkASSERT(fIntervals.empty() || fIntervals.back().fP1 == p0);
- prev = curr;
- prev_pos = curr_pos;
- curr += direction;
- } while (prev != last_index);
- // pin the last pos to maintain accurate [0,1] pos coverage.
- fIntervals.back().fP1 = last_pos;
- }
+ fIntervals.emplace_back(pack_color(c0, fColorsArePremul),
+ p0,
+ pack_color(c1, fColorsArePremul),
+ p1,
+ componentScale);
+ });
if (shader.fTileMode == SkShader::kClamp_TileMode) {
// synthetic edge interval: Pn .. +/-inf
@@ -206,36 +252,34 @@ GradientShaderBase4fContext::GradientShaderBase4fContext(const SkGradientShaderB
fIntervals.emplace_back(clamp_color, last_pos,
clamp_color, clamp_pos,
componentScale);
- } else if (shader.fTileMode == SkShader::kMirror_TileMode) {
- const int count = fIntervals.count();
- // synthetic flipped intervals in [1 .. 2)
- for (int i = count - 1; i >= 0; --i) {
- const Interval& interval = fIntervals[i];
- const SkScalar p0 = interval.fP0;
- const SkScalar p1 = interval.fP1;
- Sk4f dc = Sk4f::Load(interval.fDc.fVec);
- Sk4f c = Sk4f::Load(interval.fC0.fVec) + dc * Sk4f(p1 - p0);
- fIntervals.emplace_back(c, dc * Sk4f(-1), 2 - p1, 2 - p0);
- }
-
- if (!dx_is_pos) {
- // When dx is negative, our initial invervals are in (1..0] order.
- // The loop above appends their flipped counterparts, pivoted in 2: (1..0](2..1]
- // To achieve the expected monotonic interval order, we need to
- // swap the two halves: (2..1](1..0]
- // TODO: we can probably avoid this late swap with some additional logic during
- // the initial interval buildup.
- SkASSERT(fIntervals.count() == count * 2)
- for (int i = 0; i < count; ++i) {
- SkTSwap(fIntervals[i], fIntervals[count + i]);
- }
- }
+ } else if (shader.fTileMode == SkShader::kMirror_TileMode && dx_is_pos) {
+ // synthetic mirror intervals injected after main intervals: [1 .. 2)
+ addMirrorIntervals(shader, componentScale, dx_is_pos);
}
SkASSERT(fIntervals.count() > 0);
fCachedInterval = fIntervals.begin();
}
+void SkGradientShaderBase::
+GradientShaderBase4fContext::addMirrorIntervals(const SkGradientShaderBase& shader,
+ const Sk4f& componentScale, bool dx_is_pos) {
+ // Iterates in reverse order (vs main interval builder) and adds intervals reflected in 2.
+ const IntervalBuilder builder(shader.fOrigColors,
+ shader.fOrigPos,
+ shader.fColorCount,
+ dx_is_pos);
+ builder.build([this, &componentScale] (SkColor c0, SkColor c1, SkScalar p0, SkScalar p1) {
+ SkASSERT(fIntervals.empty() || fIntervals.back().fP1 == 2 - p0);
+
+ fIntervals.emplace_back(pack_color(c0, fColorsArePremul),
+ 2 - p0,
+ pack_color(c1, fColorsArePremul),
+ 2 - p1,
+ componentScale);
+ });
+}
+
const SkGradientShaderBase::GradientShaderBase4fContext::Interval*
SkGradientShaderBase::
GradientShaderBase4fContext::findInterval(SkScalar fx) const {
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