Avoid 2PtConical gradient flipping
Currently, when startRadius > endRadius conical gradients are inverting their data
(start/end points and radii, colors and positions) to guarantee r0 < r1 at raster time.
But the radii ordering is only mildly interesting to the impl: it controls which of the
two quadratic solutions we select for the inside case, but doesn't fundamentally change
the algorithm.
Furthermore, for the "outside" case, inverting the order is already inconvenient and
needs to be taken into account (both CPU/GPU impls are already tracking this bit of
info).
Instead of transforming the gradient definition, we can detect the inverted case and
adjust the quadratic solution selector.
In practice this means:
* |edge| case - no change, the equation is linear
* |inside| case - select the smaller root instead of largest
* |outside| case - [gpu-only] invert the clamp/limiting function
Change-Id: Ie3106464e39a4dd3848dc43671d973f7e1958e63
Reviewed-on: https://skia-review.googlesource.com/61660
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/src/shaders/gradients/SkTwoPointConicalGradient.cpp b/src/shaders/gradients/SkTwoPointConicalGradient.cpp
index a163472..04448b4 100644
--- a/src/shaders/gradients/SkTwoPointConicalGradient.cpp
+++ b/src/shaders/gradients/SkTwoPointConicalGradient.cpp
@@ -12,14 +12,15 @@
sk_sp<SkShader> SkTwoPointConicalGradient::Create(const SkPoint& c0, SkScalar r0,
const SkPoint& c1, SkScalar r1,
- bool flipped, const Descriptor& desc) {
+ const Descriptor& desc) {
SkMatrix gradientMatrix;
Type gradientType;
if (SkScalarNearlyZero((c0 - c1).length())) {
// Concentric case: we can pretend we're radial (with a tiny twist).
+ const SkScalar scale = 1.0f / SkTMax(r0, r1);
gradientMatrix = SkMatrix::MakeTrans(-c1.x(), -c1.y());
- gradientMatrix.postScale(1 / r1, 1 / r1);
+ gradientMatrix.postScale(scale, scale);
gradientType = Type::kRadial;
} else {
@@ -35,21 +36,19 @@
gradientType = Type::kTwoPoint;
}
- return sk_sp<SkShader>(new SkTwoPointConicalGradient(c0, r0, c1, r1, flipped, desc,
+ return sk_sp<SkShader>(new SkTwoPointConicalGradient(c0, r0, c1, r1, desc,
gradientType, gradientMatrix));
}
SkTwoPointConicalGradient::SkTwoPointConicalGradient(
const SkPoint& start, SkScalar startRadius,
const SkPoint& end, SkScalar endRadius,
- bool flippedGrad, const Descriptor& desc,
- Type type, const SkMatrix& gradientMatrix)
+ const Descriptor& desc, Type type, const SkMatrix& gradientMatrix)
: SkGradientShaderBase(desc, gradientMatrix)
, fCenter1(start)
, fCenter2(end)
, fRadius1(startRadius)
, fRadius2(endRadius)
- , fFlippedGrad(flippedGrad)
, fType(type)
{
// this is degenerate, and should be caught by our caller
@@ -64,18 +63,13 @@
}
// Returns the original non-sorted version of the gradient
-SkShader::GradientType SkTwoPointConicalGradient::asAGradient(
- GradientInfo* info) const {
+SkShader::GradientType SkTwoPointConicalGradient::asAGradient(GradientInfo* info) const {
if (info) {
- commonAsAGradient(info, fFlippedGrad);
+ commonAsAGradient(info);
info->fPoint[0] = fCenter1;
info->fPoint[1] = fCenter2;
info->fRadius[0] = fRadius1;
info->fRadius[1] = fRadius2;
- if (fFlippedGrad) {
- SkTSwap(info->fPoint[0], info->fPoint[1]);
- SkTSwap(info->fRadius[0], info->fRadius[1]);
- }
}
return kConical_GradientType;
}
@@ -90,7 +84,8 @@
SkScalar r1 = buffer.readScalar();
SkScalar r2 = buffer.readScalar();
- if (buffer.readBool()) { // flipped
+ if (buffer.isVersionLT(SkReadBuffer::k2PtConicalNoFlip_Version) && buffer.readBool()) {
+ // legacy flipped gradient
SkTSwap(c1, c2);
SkTSwap(r1, r2);
@@ -125,7 +120,6 @@
buffer.writePoint(fCenter2);
buffer.writeScalar(fRadius1);
buffer.writeScalar(fRadius2);
- buffer.writeBool(fFlippedGrad);
}
#if SK_SUPPORT_GPU
@@ -150,29 +144,11 @@
#endif
sk_sp<SkShader> SkTwoPointConicalGradient::onMakeColorSpace(SkColorSpaceXformer* xformer) const {
- SkSTArray<8, SkColor> origColorsStorage(fColorCount);
- SkSTArray<8, SkScalar> origPosStorage(fColorCount);
- SkSTArray<8, SkColor> xformedColorsStorage(fColorCount);
- SkColor* origColors = origColorsStorage.begin();
- SkScalar* origPos = fOrigPos ? origPosStorage.begin() : nullptr;
- SkColor* xformedColors = xformedColorsStorage.begin();
-
- // Flip if necessary
- SkPoint center1 = fFlippedGrad ? fCenter2 : fCenter1;
- SkPoint center2 = fFlippedGrad ? fCenter1 : fCenter2;
- SkScalar radius1 = fFlippedGrad ? fRadius2 : fRadius1;
- SkScalar radius2 = fFlippedGrad ? fRadius1 : fRadius2;
- for (int i = 0; i < fColorCount; i++) {
- origColors[i] = fFlippedGrad ? fOrigColors[fColorCount - i - 1] : fOrigColors[i];
- if (origPos) {
- origPos[i] = fFlippedGrad ? 1.0f - fOrigPos[fColorCount - i - 1] : fOrigPos[i];
- }
- }
-
- xformer->apply(xformedColors, origColors, fColorCount);
- return SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2, xformedColors,
- origPos, fColorCount, fTileMode, fGradFlags,
- &this->getLocalMatrix());
+ SkSTArray<8, SkColor> xformedColors(fColorCount);
+ xformer->apply(xformedColors.begin(), fOrigColors, fColorCount);
+ return SkGradientShader::MakeTwoPointConical(fCenter1, fRadius1, fCenter2, fRadius2,
+ xformedColors.begin(), fOrigPos, fColorCount,
+ fTileMode, fGradFlags, &this->getLocalMatrix());
}
@@ -205,13 +181,12 @@
void SkTwoPointConicalGradient::appendGradientStages(SkArenaAlloc* alloc, SkRasterPipeline* p,
SkRasterPipeline* postPipeline) const {
const auto dRadius = fRadius2 - fRadius1;
- SkASSERT(dRadius >= 0);
if (fType == Type::kRadial) {
p->append(SkRasterPipeline::xy_to_radius);
// Tiny twist: radial computes a t for [0, r2], but we want a t for [r1, r2].
- auto scale = fRadius2 / dRadius;
+ auto scale = SkTMax(fRadius1, fRadius2) / dRadius;
auto bias = -fRadius1 / dRadius;
p->append_matrix(alloc, SkMatrix::Concat(SkMatrix::MakeTrans(bias, 0),
@@ -238,24 +213,21 @@
p->append(SkRasterPipeline::xy_to_2pt_conical_linear, ctx);
isWellBehaved = false;
} else {
- if (dCenter + fRadius1 > fRadius2) {
- // The focal point is outside the end circle.
+ isWellBehaved = SkScalarAbs(dRadius) >= dCenter;
+ bool isFlipped = isWellBehaved && dRadius < 0;
- // We want the larger root, per spec:
- // "For all values of ω where r(ω) > 0, starting with the value of ω nearest
- // to positive infinity and ending with the value of ω nearest to negative
- // infinity, draw the circumference of the circle with radius r(ω) at position
- // (x(ω), y(ω)), with the color at ω, but only painting on the parts of the
- // bitmap that have not yet been painted on by earlier circles in this step for
- // this rendering of the gradient."
- // (https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-createradialgradient)
- p->append(fFlippedGrad ? SkRasterPipeline::xy_to_2pt_conical_quadratic_min
- : SkRasterPipeline::xy_to_2pt_conical_quadratic_max, ctx);
- isWellBehaved = false;
- } else {
- // The focal point is inside (well-behaved case).
- p->append(SkRasterPipeline::xy_to_2pt_conical_quadratic_max, ctx);
- }
+ // We want the larger root, per spec:
+ // "For all values of ω where r(ω) > 0, starting with the value of ω nearest
+ // to positive infinity and ending with the value of ω nearest to negative
+ // infinity, draw the circumference of the circle with radius r(ω) at position
+ // (x(ω), y(ω)), with the color at ω, but only painting on the parts of the
+ // bitmap that have not yet been painted on by earlier circles in this step for
+ // this rendering of the gradient."
+ // (https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-createradialgradient)
+ //
+ // ... except when the gradient is flipped.
+ p->append(isFlipped ? SkRasterPipeline::xy_to_2pt_conical_quadratic_min
+ : SkRasterPipeline::xy_to_2pt_conical_quadratic_max, ctx);
}
if (!isWellBehaved) {