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/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "src/gpu/gradients/GrGradientShader.h"
#include "src/gpu/gradients/generated/GrClampedGradientEffect.h"
#include "src/gpu/gradients/generated/GrTiledGradientEffect.h"
#include "src/gpu/gradients/generated/GrLinearGradientLayout.h"
#include "src/gpu/gradients/generated/GrRadialGradientLayout.h"
#include "src/gpu/gradients/generated/GrSweepGradientLayout.h"
#include "src/gpu/gradients/generated/GrTwoPointConicalGradientLayout.h"
#include "src/gpu/gradients/GrGradientBitmapCache.h"
#include "src/gpu/gradients/generated/GrDualIntervalGradientColorizer.h"
#include "src/gpu/gradients/generated/GrSingleIntervalGradientColorizer.h"
#include "src/gpu/gradients/generated/GrUnrolledBinaryGradientColorizer.h"
#include "include/gpu/GrRecordingContext.h"
#include "src/gpu/GrCaps.h"
#include "src/gpu/GrColor.h"
#include "src/gpu/GrColorInfo.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/SkGr.h"
#include "src/gpu/effects/GrTextureEffect.h"
// Intervals smaller than this (that aren't hard stops) on low-precision-only devices force us to
// use the textured gradient
static const SkScalar kLowPrecisionIntervalLimit = 0.01f;
// Each cache entry costs 1K or 2K of RAM. Each bitmap will be 1x256 at either 32bpp or 64bpp.
static const int kMaxNumCachedGradientBitmaps = 32;
static const int kGradientTextureSize = 256;
// NOTE: signature takes raw pointers to the color/pos arrays and a count to make it easy for
// MakeColorizer to transparently take care of hard stops at the end points of the gradient.
static std::unique_ptr<GrFragmentProcessor> make_textured_colorizer(const SkPMColor4f* colors,
const SkScalar* positions, int count, bool premul, const GrFPArgs& args) {
static GrGradientBitmapCache gCache(kMaxNumCachedGradientBitmaps, kGradientTextureSize);
// Use 8888 or F16, depending on the destination config.
// TODO: Use 1010102 for opaque gradients, at least if destination is 1010102?
SkColorType colorType = kRGBA_8888_SkColorType;
if (GrColorTypeIsWiderThan(args.fDstColorInfo->colorType(), 8)) {
auto f16Format = args.fContext->priv().caps()->getDefaultBackendFormat(
GrColorType::kRGBA_F16, GrRenderable::kNo);
if (f16Format.isValid()) {
colorType = kRGBA_F16_SkColorType;
}
}
SkAlphaType alphaType = premul ? kPremul_SkAlphaType : kUnpremul_SkAlphaType;
SkBitmap bitmap;
gCache.getGradient(colors, positions, count, colorType, alphaType, &bitmap);
SkASSERT(1 == bitmap.height() && SkIsPow2(bitmap.width()));
SkASSERT(bitmap.isImmutable());
auto view = GrMakeCachedBitmapProxyView(args.fContext, bitmap);
if (!view.proxy()) {
SkDebugf("Gradient won't draw. Could not create texture.");
return nullptr;
}
auto m = SkMatrix::Scale(view.width(), 1.f);
return GrTextureEffect::Make(std::move(view), alphaType, m, GrSamplerState::Filter::kLinear);
}
// Analyze the shader's color stops and positions and chooses an appropriate colorizer to represent
// the gradient.
static std::unique_ptr<GrFragmentProcessor> make_colorizer(const SkPMColor4f* colors,
const SkScalar* positions, int count, bool premul, const GrFPArgs& args) {
// If there are hard stops at the beginning or end, the first and/or last color should be
// ignored by the colorizer since it should only be used in a clamped border color. By detecting
// and removing these stops at the beginning, it makes optimizing the remaining color stops
// simpler.
// SkGradientShaderBase guarantees that pos[0] == 0 by adding a dummy
bool bottomHardStop = SkScalarNearlyEqual(positions[0], positions[1]);
// The same is true for pos[end] == 1
bool topHardStop = SkScalarNearlyEqual(positions[count - 2], positions[count - 1]);
int offset = 0;
if (bottomHardStop) {
offset += 1;
count--;
}
if (topHardStop) {
count--;
}
// Two remaining colors means a single interval from 0 to 1
// (but it may have originally been a 3 or 4 color gradient with 1-2 hard stops at the ends)
if (count == 2) {
return GrSingleIntervalGradientColorizer::Make(colors[offset], colors[offset + 1]);
}
// Do an early test for the texture fallback to skip all of the other tests for specific
// analytic support of the gradient (and compatibility with the hardware), when it's definitely
// impossible to use an analytic solution.
bool tryAnalyticColorizer = count <= GrUnrolledBinaryGradientColorizer::kMaxColorCount;
// The remaining analytic colorizers use scale*t+bias, and the scale/bias values can become
// quite large when thresholds are close (but still outside the hardstop limit). If float isn't
// 32-bit, output can be incorrect if the thresholds are too close together. However, the
// analytic shaders are higher quality, so they can be used with lower precision hardware when
// the thresholds are not ill-conditioned.
const GrShaderCaps* caps = args.fContext->priv().caps()->shaderCaps();
if (!caps->floatIs32Bits() && tryAnalyticColorizer) {
// Could run into problems, check if thresholds are close together (with a limit of .01, so
// that scales will be less than 100, which leaves 4 decimals of precision on 16-bit).
for (int i = offset; i < count - 1; i++) {
SkScalar dt = SkScalarAbs(positions[i] - positions[i + 1]);
if (dt <= kLowPrecisionIntervalLimit && dt > SK_ScalarNearlyZero) {
tryAnalyticColorizer = false;
break;
}
}
}
if (tryAnalyticColorizer) {
if (count == 3) {
// Must be a dual interval gradient, where the middle point is at offset+1 and the two
// intervals share the middle color stop.
return GrDualIntervalGradientColorizer::Make(colors[offset], colors[offset + 1],
colors[offset + 1], colors[offset + 2],
positions[offset + 1]);
} else if (count == 4 && SkScalarNearlyEqual(positions[offset + 1],
positions[offset + 2])) {
// Two separate intervals that join at the same threshold position
return GrDualIntervalGradientColorizer::Make(colors[offset], colors[offset + 1],
colors[offset + 2], colors[offset + 3],
positions[offset + 1]);
}
// The single and dual intervals are a specialized case of the unrolled binary search
// colorizer which can analytically render gradients of up to 8 intervals (up to 9 or 16
// colors depending on how many hard stops are inserted).
std::unique_ptr<GrFragmentProcessor> unrolled = GrUnrolledBinaryGradientColorizer::Make(
colors + offset, positions + offset, count);
if (unrolled) {
return unrolled;
}
}
// Otherwise fall back to a rasterized gradient sampled by a texture, which can handle
// arbitrary gradients (the only downside being sampling resolution).
return make_textured_colorizer(colors + offset, positions + offset, count, premul, args);
}
// Combines the colorizer and layout with an appropriately configured master effect based on the
// gradient's tile mode
static std::unique_ptr<GrFragmentProcessor> make_gradient(const SkGradientShaderBase& shader,
const GrFPArgs& args, std::unique_ptr<GrFragmentProcessor> layout) {
// No shader is possible if a layout couldn't be created, e.g. a layout-specific Make() returned
// null.
if (layout == nullptr) {
return nullptr;
}
// Convert all colors into destination space and into SkPMColor4fs, and handle
// premul issues depending on the interpolation mode
bool inputPremul = shader.getGradFlags() & SkGradientShader::kInterpolateColorsInPremul_Flag;
bool allOpaque = true;
SkAutoSTMalloc<4, SkPMColor4f> colors(shader.fColorCount);
SkColor4fXformer xformedColors(shader.fOrigColors4f, shader.fColorCount,
shader.fColorSpace.get(), args.fDstColorInfo->colorSpace());
for (int i = 0; i < shader.fColorCount; i++) {
const SkColor4f& upmColor = xformedColors.fColors[i];
colors[i] = inputPremul ? upmColor.premul()
: SkPMColor4f{ upmColor.fR, upmColor.fG, upmColor.fB, upmColor.fA };
if (allOpaque && !SkScalarNearlyEqual(colors[i].fA, 1.0)) {
allOpaque = false;
}
}
// SkGradientShader stores positions implicitly when they are evenly spaced, but the getPos()
// implementation performs a branch for every position index. Since the shader conversion
// requires lots of position tests, calculate all of the positions up front if needed.
SkTArray<SkScalar, true> implicitPos;
SkScalar* positions;
if (shader.fOrigPos) {
positions = shader.fOrigPos;
} else {
implicitPos.reserve(shader.fColorCount);
SkScalar posScale = SK_Scalar1 / (shader.fColorCount - 1);
for (int i = 0 ; i < shader.fColorCount; i++) {
implicitPos.push_back(SkIntToScalar(i) * posScale);
}
positions = implicitPos.begin();
}
// All gradients are colorized the same way, regardless of layout
std::unique_ptr<GrFragmentProcessor> colorizer = make_colorizer(
colors.get(), positions, shader.fColorCount, inputPremul, args);
if (colorizer == nullptr) {
return nullptr;
}
// The master effect has to export premul colors, but under certain conditions it doesn't need
// to do anything to achieve that: i.e. its interpolating already premul colors (inputPremul)
// or all the colors have a = 1, in which case premul is a no op. Note that this allOpaque
// check is more permissive than SkGradientShaderBase's isOpaque(), since we can optimize away
// the make-premul op for two point conical gradients (which report false for isOpaque).
bool makePremul = !inputPremul && !allOpaque;
// All tile modes are supported (unless something was added to SkShader)
std::unique_ptr<GrFragmentProcessor> master;
switch(shader.getTileMode()) {
case SkTileMode::kRepeat:
master = GrTiledGradientEffect::Make(std::move(colorizer), std::move(layout),
/* mirror */ false, makePremul, allOpaque);
break;
case SkTileMode::kMirror:
master = GrTiledGradientEffect::Make(std::move(colorizer), std::move(layout),
/* mirror */ true, makePremul, allOpaque);
break;
case SkTileMode::kClamp:
// For the clamped mode, the border colors are the first and last colors, corresponding
// to t=0 and t=1, because SkGradientShaderBase enforces that by adding color stops as
// appropriate. If there is a hard stop, this grabs the expected outer colors for the
// border.
master = GrClampedGradientEffect::Make(std::move(colorizer), std::move(layout),
colors[0], colors[shader.fColorCount - 1], makePremul, allOpaque);
break;
case SkTileMode::kDecal:
// Even if the gradient colors are opaque, the decal borders are transparent so
// disable that optimization
master = GrClampedGradientEffect::Make(std::move(colorizer), std::move(layout),
SK_PMColor4fTRANSPARENT, SK_PMColor4fTRANSPARENT,
makePremul, /* colorsAreOpaque */ false);
break;
}
if (master == nullptr) {
// Unexpected tile mode
return nullptr;
}
if (args.fInputColorIsOpaque) {
return GrFragmentProcessor::OverrideInput(std::move(master), SK_PMColor4fWHITE, false);
}
return GrFragmentProcessor::MulChildByInputAlpha(std::move(master));
}
namespace GrGradientShader {
std::unique_ptr<GrFragmentProcessor> MakeLinear(const SkLinearGradient& shader,
const GrFPArgs& args) {
return make_gradient(shader, args, GrLinearGradientLayout::Make(shader, args));
}
std::unique_ptr<GrFragmentProcessor> MakeRadial(const SkRadialGradient& shader,
const GrFPArgs& args) {
return make_gradient(shader,args, GrRadialGradientLayout::Make(shader, args));
}
std::unique_ptr<GrFragmentProcessor> MakeSweep(const SkSweepGradient& shader,
const GrFPArgs& args) {
return make_gradient(shader,args, GrSweepGradientLayout::Make(shader, args));
}
std::unique_ptr<GrFragmentProcessor> MakeConical(const SkTwoPointConicalGradient& shader,
const GrFPArgs& args) {
return make_gradient(shader, args, GrTwoPointConicalGradientLayout::Make(shader, args));
}
#if GR_TEST_UTILS
RandomParams::RandomParams(SkRandom* random) {
// Set color count to min of 2 so that we don't trigger the const color optimization and make
// a non-gradient processor.
fColorCount = random->nextRangeU(2, kMaxRandomGradientColors);
fUseColors4f = random->nextBool();
// if one color, omit stops, otherwise randomly decide whether or not to
if (fColorCount == 1 || (fColorCount >= 2 && random->nextBool())) {
fStops = nullptr;
} else {
fStops = fStopStorage;
}
// if using SkColor4f, attach a random (possibly null) color space (with linear gamma)
if (fUseColors4f) {
fColorSpace = GrTest::TestColorSpace(random);
}
SkScalar stop = 0.f;
for (int i = 0; i < fColorCount; ++i) {
if (fUseColors4f) {
fColors4f[i].fR = random->nextUScalar1();
fColors4f[i].fG = random->nextUScalar1();
fColors4f[i].fB = random->nextUScalar1();
fColors4f[i].fA = random->nextUScalar1();
} else {
fColors[i] = random->nextU();
}
if (fStops) {
fStops[i] = stop;
stop = i < fColorCount - 1 ? stop + random->nextUScalar1() * (1.f - stop) : 1.f;
}
}
fTileMode = static_cast<SkTileMode>(random->nextULessThan(kSkTileModeCount));
}
#endif
}