Use the 4f impl for legacy/8888 linear gradients
This is a partial revert of https://skia-review.googlesource.com/c/20280,
adding back L32 support for 4f gradients and switching off the legacy
impl.
If it sticks, we should be able to completely delete the legacy gradient
code.
Change-Id: Iaa6d722ea4dfd8e4d959bb76eca815a30ca7098f
Reviewed-on: https://skia-review.googlesource.com/31425
Reviewed-by: Herb Derby <herb@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/src/shaders/gradients/Sk4fLinearGradient.cpp b/src/shaders/gradients/Sk4fLinearGradient.cpp
index 700b7fb..11bf96d 100644
--- a/src/shaders/gradients/Sk4fLinearGradient.cpp
+++ b/src/shaders/gradients/Sk4fLinearGradient.cpp
@@ -12,20 +12,21 @@
namespace {
-template<ApplyPremul premul>
-void ramp(const Sk4f& c, const Sk4f& dc, SkPM4f dst[], int n) {
+template<typename dstType, ApplyPremul premul>
+void ramp(const Sk4f& c, const Sk4f& dc, dstType dst[], int n,
+ const Sk4f& bias0, const Sk4f& bias1) {
SkASSERT(n > 0);
- const Sk4f dc2 = dc + dc;
- const Sk4f dc4 = dc2 + dc2;
+ const Sk4f dc2 = dc + dc,
+ dc4 = dc2 + dc2;
- Sk4f c0 = c ;
- Sk4f c1 = c + dc;
- Sk4f c2 = c0 + dc2;
- Sk4f c3 = c1 + dc2;
+ Sk4f c0 = c + DstTraits<dstType, premul>::pre_lerp_bias(bias0),
+ c1 = c + dc + DstTraits<dstType, premul>::pre_lerp_bias(bias1),
+ c2 = c0 + dc2,
+ c3 = c1 + dc2;
while (n >= 4) {
- DstTraits<premul>::store4x(c0, c1, c2, c3, dst);
+ DstTraits<dstType, premul>::store4x(c0, c1, c2, c3, dst, bias0, bias1);
dst += 4;
c0 = c0 + dc4;
@@ -35,12 +36,12 @@
n -= 4;
}
if (n & 2) {
- DstTraits<premul>::store(c0, dst++);
- DstTraits<premul>::store(c1, dst++);
+ DstTraits<dstType, premul>::store(c0, dst++, bias0);
+ DstTraits<dstType, premul>::store(c1, dst++, bias1);
c0 = c0 + dc2;
}
if (n & 1) {
- DstTraits<premul>::store(c0, dst);
+ DstTraits<dstType, premul>::store(c0, dst, bias0);
}
}
@@ -141,37 +142,81 @@
}
}
+
+void SkLinearGradient::
+LinearGradient4fContext::shadeSpan(int x, int y, SkPMColor dst[], int count) {
+ SkASSERT(count > 0);
+
+ float bias0 = 0,
+ bias1 = 0;
+
+ if (fDither) {
+ static constexpr float dither_cell[] = {
+ -3/8.0f, 1/8.0f,
+ 3/8.0f, -1/8.0f,
+ };
+
+ const int rowIndex = (y & 1) << 1;
+ bias0 = dither_cell[rowIndex + 0];
+ bias1 = dither_cell[rowIndex + 1];
+
+ if (x & 1) {
+ SkTSwap(bias0, bias1);
+ }
+ }
+
+ if (fColorsArePremul) {
+ // In premul interpolation mode, components are pre-scaled by 255 and the store
+ // op is truncating. We pre-bias here to achieve rounding.
+ bias0 += 0.5f;
+ bias1 += 0.5f;
+
+ this->shadePremulSpan<SkPMColor, ApplyPremul::False>(x, y, dst, count, bias0, bias1);
+ } else {
+ // In unpremul interpolation mode, Components are not pre-scaled.
+ bias0 *= 1/255.0f;
+ bias1 *= 1/255.0f;
+
+ this->shadePremulSpan<SkPMColor, ApplyPremul::True >(x, y, dst, count, bias0, bias1);
+ }
+}
+
void SkLinearGradient::
LinearGradient4fContext::shadeSpan4f(int x, int y, SkPM4f dst[], int count) {
SkASSERT(count > 0);
+
+ // 4f dests are dithered at a later stage, if needed.
+ static constexpr float bias0 = 0,
+ bias1 = 0;
if (fColorsArePremul) {
- this->shadePremulSpan<ApplyPremul::False>(x, y, dst, count);
+ this->shadePremulSpan<SkPM4f, ApplyPremul::False>(x, y, dst, count, bias0, bias1);
} else {
- this->shadePremulSpan<ApplyPremul::True>(x, y, dst, count);
+ this->shadePremulSpan<SkPM4f, ApplyPremul::True >(x, y, dst, count, bias0, bias1);
}
}
-template<ApplyPremul premul>
+template<typename dstType, ApplyPremul premul>
void SkLinearGradient::
-LinearGradient4fContext::shadePremulSpan(int x, int y, SkPM4f dst[], int count) const {
- const SkLinearGradient& shader =
- static_cast<const SkLinearGradient&>(fShader);
+LinearGradient4fContext::shadePremulSpan(int x, int y, dstType dst[], int count,
+ float bias0, float bias1) const {
+ const SkLinearGradient& shader = static_cast<const SkLinearGradient&>(fShader);
switch (shader.fTileMode) {
case kClamp_TileMode:
- this->shadeSpanInternal<premul, kClamp_TileMode>(x, y, dst, count);
+ this->shadeSpanInternal<dstType, premul, kClamp_TileMode >(x, y, dst, count, bias0, bias1);
break;
case kRepeat_TileMode:
- this->shadeSpanInternal<premul, kRepeat_TileMode>(x, y, dst, count);
+ this->shadeSpanInternal<dstType, premul, kRepeat_TileMode>(x, y, dst, count, bias0, bias1);
break;
case kMirror_TileMode:
- this->shadeSpanInternal<premul, kMirror_TileMode>(x, y, dst, count);
+ this->shadeSpanInternal<dstType, premul, kMirror_TileMode>(x, y, dst, count, bias0, bias1);
break;
}
}
-template<ApplyPremul premul, SkShader::TileMode tileMode>
+template<typename dstType, ApplyPremul premul, SkShader::TileMode tileMode>
void SkLinearGradient::
-LinearGradient4fContext::shadeSpanInternal(int x, int y, SkPM4f dst[], int count) const {
+LinearGradient4fContext::shadeSpanInternal(int x, int y, dstType dst[], int count,
+ float bias0, float bias1) const {
SkPoint pt;
fDstToPosProc(fDstToPos,
x + SK_ScalarHalf,
@@ -179,12 +224,15 @@
&pt);
const SkScalar fx = pinFx<tileMode>(pt.x());
const SkScalar dx = fDstToPos.getScaleX();
- LinearIntervalProcessor<premul, tileMode> proc(fIntervals->begin(),
- fIntervals->end() - 1,
- this->findInterval(fx),
- fx,
- dx,
- SkScalarNearlyZero(dx * count));
+ LinearIntervalProcessor<dstType, premul, tileMode> proc(fIntervals->begin(),
+ fIntervals->end() - 1,
+ this->findInterval(fx),
+ fx,
+ dx,
+ SkScalarNearlyZero(dx * count));
+ Sk4f bias4f0(bias0),
+ bias4f1(bias1);
+
while (count > 0) {
// What we really want here is SkTPin(advance, 1, count)
// but that's a significant perf hit for >> stops; investigate.
@@ -199,18 +247,23 @@
|| (n == count && proc.currentRampIsZero()));
if (proc.currentRampIsZero()) {
- DstTraits<premul>::store(proc.currentColor(), dst, n);
+ DstTraits<dstType, premul>::store(proc.currentColor(), dst, n);
} else {
- ramp<premul>(proc.currentColor(), proc.currentColorGrad(), dst, n);
+ ramp<dstType, premul>(proc.currentColor(), proc.currentColorGrad(), dst, n,
+ bias4f0, bias4f1);
}
proc.advance(SkIntToScalar(n));
count -= n;
dst += n;
+
+ if (n & 1) {
+ SkTSwap(bias4f0, bias4f1);
+ }
}
}
-template<ApplyPremul premul, SkShader::TileMode tileMode>
+template<typename dstType, ApplyPremul premul, SkShader::TileMode tileMode>
class SkLinearGradient::
LinearGradient4fContext::LinearIntervalProcessor {
public:
@@ -275,8 +328,8 @@
void compute_interval_props(SkScalar t) {
SkASSERT(in_range(t, fInterval->fT0, fInterval->fT1));
- const Sk4f dc = DstTraits<premul>::load(fInterval->fCg);
- fCc = DstTraits<premul>::load(fInterval->fCb) + dc * Sk4f(t);
+ const Sk4f dc = DstTraits<dstType, premul>::load(fInterval->fCg);
+ fCc = DstTraits<dstType, premul>::load(fInterval->fCb) + dc * Sk4f(t);
fDcDx = dc * fDx;
fZeroRamp = fIsVertical || (dc == 0).allTrue();
}
@@ -295,8 +348,8 @@
//
// Avg += C * (t1 - t0)
//
- const auto c = DstTraits<premul>::load(i->fCb)
- + DstTraits<premul>::load(i->fCg) * (i->fT0 + i->fT1) * 0.5f;
+ const auto c = DstTraits<dstType, premul>::load(i->fCb)
+ + DstTraits<dstType, premul>::load(i->fCg) * (i->fT0 + i->fT1) * 0.5f;
fCc = fCc + c * (i->fT1 - i->fT0);
}
}