move blur impl into core

Ever since we added drawShadow to the public api, blurs have necessarily
part of the core. This CL just formalizes that.

This should also allow us to have builds that exclude all of /effects (for code size)
and still be valid.

Will follow-up with a change to deprecate SkBlurMaskFilter and SkBlurQuality (both no longer needed).

Bug: skia:
Change-Id: Ifbbd8b47a30a0386d215726b67bcf1e8b84fb8f5
Reviewed-on: https://skia-review.googlesource.com/113713
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 349 insertions, 0 deletions

diff --git a/src/gpu/effects/GrCircleBlurFragmentProcessor.cpp b/src/gpu/effects/GrCircleBlurFragmentProcessor.cpp
new file mode 100644
index 0000000000..d44f431dd3
--- /dev/null
+++ b/src/gpu/effects/GrCircleBlurFragmentProcessor.cpp
@@ -0,0 +1,349 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/**************************************************************************************************
+ *** This file was autogenerated from GrCircleBlurFragmentProcessor.fp; do not modify.
+ **************************************************************************************************/
+#include "GrCircleBlurFragmentProcessor.h"
+#if SK_SUPPORT_GPU
+
+#include "GrProxyProvider.h"
+
+// Computes an unnormalized half kernel (right side). Returns the summation of all the half
+// kernel values.
+static float make_unnormalized_half_kernel(float* halfKernel, int halfKernelSize, float sigma) {
+    const float invSigma = 1.f / sigma;
+    const float b = -0.5f * invSigma * invSigma;
+    float tot = 0.0f;
+    // Compute half kernel values at half pixel steps out from the center.
+    float t = 0.5f;
+    for (int i = 0; i < halfKernelSize; ++i) {
+        float value = expf(t * t * b);
+        tot += value;
+        halfKernel[i] = value;
+        t += 1.f;
+    }
+    return tot;
+}
+
+// Create a Gaussian half-kernel (right side) and a summed area table given a sigma and number
+// of discrete steps. The half kernel is normalized to sum to 0.5.
+static void make_half_kernel_and_summed_table(float* halfKernel, float* summedHalfKernel,
+                                              int halfKernelSize, float sigma) {
+    // The half kernel should sum to 0.5 not 1.0.
+    const float tot = 2.f * make_unnormalized_half_kernel(halfKernel, halfKernelSize, sigma);
+    float sum = 0.f;
+    for (int i = 0; i < halfKernelSize; ++i) {
+        halfKernel[i] /= tot;
+        sum += halfKernel[i];
+        summedHalfKernel[i] = sum;
+    }
+}
+
+// Applies the 1D half kernel vertically at points along the x axis to a circle centered at the
+// origin with radius circleR.
+void apply_kernel_in_y(float* results, int numSteps, float firstX, float circleR,
+                       int halfKernelSize, const float* summedHalfKernelTable) {
+    float x = firstX;
+    for (int i = 0; i < numSteps; ++i, x += 1.f) {
+        if (x < -circleR || x > circleR) {
+            results[i] = 0;
+            continue;
+        }
+        float y = sqrtf(circleR * circleR - x * x);
+        // In the column at x we exit the circle at +y and -y
+        // The summed table entry j is actually reflects an offset of j + 0.5.
+        y -= 0.5f;
+        int yInt = SkScalarFloorToInt(y);
+        SkASSERT(yInt >= -1);
+        if (y < 0) {
+            results[i] = (y + 0.5f) * summedHalfKernelTable[0];
+        } else if (yInt >= halfKernelSize - 1) {
+            results[i] = 0.5f;
+        } else {
+            float yFrac = y - yInt;
+            results[i] = (1.f - yFrac) * summedHalfKernelTable[yInt] +
+                         yFrac * summedHalfKernelTable[yInt + 1];
+        }
+    }
+}
+
+// Apply a Gaussian at point (evalX, 0) to a circle centered at the origin with radius circleR.
+// This relies on having a half kernel computed for the Gaussian and a table of applications of
+// the half kernel in y to columns at (evalX - halfKernel, evalX - halfKernel + 1, ..., evalX +
+// halfKernel) passed in as yKernelEvaluations.
+static uint8_t eval_at(float evalX, float circleR, const float* halfKernel, int halfKernelSize,
+                       const float* yKernelEvaluations) {
+    float acc = 0;
+
+    float x = evalX - halfKernelSize;
+    for (int i = 0; i < halfKernelSize; ++i, x += 1.f) {
+        if (x < -circleR || x > circleR) {
+            continue;
+        }
+        float verticalEval = yKernelEvaluations[i];
+        acc += verticalEval * halfKernel[halfKernelSize - i - 1];
+    }
+    for (int i = 0; i < halfKernelSize; ++i, x += 1.f) {
+        if (x < -circleR || x > circleR) {
+            continue;
+        }
+        float verticalEval = yKernelEvaluations[i + halfKernelSize];
+        acc += verticalEval * halfKernel[i];
+    }
+    // Since we applied a half kernel in y we multiply acc by 2 (the circle is symmetric about
+    // the x axis).
+    return SkUnitScalarClampToByte(2.f * acc);
+}
+
+// This function creates a profile of a blurred circle. It does this by computing a kernel for
+// half the Gaussian and a matching summed area table. The summed area table is used to compute
+// an array of vertical applications of the half kernel to the circle along the x axis. The
+// table of y evaluations has 2 * k + n entries where k is the size of the half kernel and n is
+// the size of the profile being computed. Then for each of the n profile entries we walk out k
+// steps in each horizontal direction multiplying the corresponding y evaluation by the half
+// kernel entry and sum these values to compute the profile entry.
+static void create_circle_profile(uint8_t* weights, float sigma, float circleR,
+                                  int profileTextureWidth) {
+    const int numSteps = profileTextureWidth;
+
+    // The full kernel is 6 sigmas wide.
+    int halfKernelSize = SkScalarCeilToInt(6.0f * sigma);
+    // round up to next multiple of 2 and then divide by 2
+    halfKernelSize = ((halfKernelSize + 1) & ~1) >> 1;
+
+    // Number of x steps at which to apply kernel in y to cover all the profile samples in x.
+    int numYSteps = numSteps + 2 * halfKernelSize;
+
+    SkAutoTArray<float> bulkAlloc(halfKernelSize + halfKernelSize + numYSteps);
+    float* halfKernel = bulkAlloc.get();
+    float* summedKernel = bulkAlloc.get() + halfKernelSize;
+    float* yEvals = bulkAlloc.get() + 2 * halfKernelSize;
+    make_half_kernel_and_summed_table(halfKernel, summedKernel, halfKernelSize, sigma);
+
+    float firstX = -halfKernelSize + 0.5f;
+    apply_kernel_in_y(yEvals, numYSteps, firstX, circleR, halfKernelSize, summedKernel);
+
+    for (int i = 0; i < numSteps - 1; ++i) {
+        float evalX = i + 0.5f;
+        weights[i] = eval_at(evalX, circleR, halfKernel, halfKernelSize, yEvals + i);
+    }
+    // Ensure the tail of the Gaussian goes to zero.
+    weights[numSteps - 1] = 0;
+}
+
+static void create_half_plane_profile(uint8_t* profile, int profileWidth) {
+    SkASSERT(!(profileWidth & 0x1));
+    // The full kernel is 6 sigmas wide.
+    float sigma = profileWidth / 6.f;
+    int halfKernelSize = profileWidth / 2;
+
+    SkAutoTArray<float> halfKernel(halfKernelSize);
+
+    // The half kernel should sum to 0.5.
+    const float tot = 2.f * make_unnormalized_half_kernel(halfKernel.get(), halfKernelSize, sigma);
+    float sum = 0.f;
+    // Populate the profile from the right edge to the middle.
+    for (int i = 0; i < halfKernelSize; ++i) {
+        halfKernel[halfKernelSize - i - 1] /= tot;
+        sum += halfKernel[halfKernelSize - i - 1];
+        profile[profileWidth - i - 1] = SkUnitScalarClampToByte(sum);
+    }
+    // Populate the profile from the middle to the left edge (by flipping the half kernel and
+    // continuing the summation).
+    for (int i = 0; i < halfKernelSize; ++i) {
+        sum += halfKernel[i];
+        profile[halfKernelSize - i - 1] = SkUnitScalarClampToByte(sum);
+    }
+    // Ensure tail goes to 0.
+    profile[profileWidth - 1] = 0;
+}
+
+static sk_sp<GrTextureProxy> create_profile_texture(GrProxyProvider* proxyProvider,
+                                                    const SkRect& circle, float sigma,
+                                                    float* solidRadius, float* textureRadius) {
+    float circleR = circle.width() / 2.0f;
+    if (circleR < SK_ScalarNearlyZero) {
+        return nullptr;
+    }
+    // Profile textures are cached by the ratio of sigma to circle radius and by the size of the
+    // profile texture (binned by powers of 2).
+    SkScalar sigmaToCircleRRatio = sigma / circleR;
+    // When sigma is really small this becomes a equivalent to convolving a Gaussian with a
+    // half-plane. Similarly, in the extreme high ratio cases circle becomes a point WRT to the
+    // Guassian and the profile texture is a just a Gaussian evaluation. However, we haven't yet
+    // implemented this latter optimization.
+    sigmaToCircleRRatio = SkTMin(sigmaToCircleRRatio, 8.f);
+    SkFixed sigmaToCircleRRatioFixed;
+    static const SkScalar kHalfPlaneThreshold = 0.1f;
+    bool useHalfPlaneApprox = false;
+    if (sigmaToCircleRRatio <= kHalfPlaneThreshold) {
+        useHalfPlaneApprox = true;
+        sigmaToCircleRRatioFixed = 0;
+        *solidRadius = circleR - 3 * sigma;
+        *textureRadius = 6 * sigma;
+    } else {
+        // Convert to fixed point for the key.
+        sigmaToCircleRRatioFixed = SkScalarToFixed(sigmaToCircleRRatio);
+        // We shave off some bits to reduce the number of unique entries. We could probably
+        // shave off more than we do.
+        sigmaToCircleRRatioFixed &= ~0xff;
+        sigmaToCircleRRatio = SkFixedToScalar(sigmaToCircleRRatioFixed);
+        sigma = circleR * sigmaToCircleRRatio;
+        *solidRadius = 0;
+        *textureRadius = circleR + 3 * sigma;
+    }
+
+    static const GrUniqueKey::Domain kDomain = GrUniqueKey::GenerateDomain();
+    GrUniqueKey key;
+    GrUniqueKey::Builder builder(&key, kDomain, 1);
+    builder[0] = sigmaToCircleRRatioFixed;
+    builder.finish();
+
+    sk_sp<GrTextureProxy> blurProfile =
+            proxyProvider->findOrCreateProxyByUniqueKey(key, kTopLeft_GrSurfaceOrigin);
+    if (!blurProfile) {
+        static constexpr int kProfileTextureWidth = 512;
+
+        SkBitmap bm;
+        if (!bm.tryAllocPixels(SkImageInfo::MakeA8(kProfileTextureWidth, 1))) {
+            return nullptr;
+        }
+
+        if (useHalfPlaneApprox) {
+            create_half_plane_profile(bm.getAddr8(0, 0), kProfileTextureWidth);
+        } else {
+            // Rescale params to the size of the texture we're creating.
+            SkScalar scale = kProfileTextureWidth / *textureRadius;
+            create_circle_profile(bm.getAddr8(0, 0), sigma * scale, circleR * scale,
+                                  kProfileTextureWidth);
+        }
+
+        bm.setImmutable();
+        sk_sp<SkImage> image = SkImage::MakeFromBitmap(bm);
+
+        blurProfile = proxyProvider->createTextureProxy(std::move(image), kNone_GrSurfaceFlags, 1,
+                                                        SkBudgeted::kYes, SkBackingFit::kExact);
+        if (!blurProfile) {
+            return nullptr;
+        }
+
+        SkASSERT(blurProfile->origin() == kTopLeft_GrSurfaceOrigin);
+        proxyProvider->assignUniqueKeyToProxy(key, blurProfile.get());
+    }
+
+    return blurProfile;
+}
+
+std::unique_ptr<GrFragmentProcessor> GrCircleBlurFragmentProcessor::Make(
+        GrProxyProvider* proxyProvider, const SkRect& circle, float sigma) {
+    float solidRadius;
+    float textureRadius;
+    sk_sp<GrTextureProxy> profile(
+            create_profile_texture(proxyProvider, circle, sigma, &solidRadius, &textureRadius));
+    if (!profile) {
+        return nullptr;
+    }
+    return std::unique_ptr<GrFragmentProcessor>(new GrCircleBlurFragmentProcessor(
+            circle, textureRadius, solidRadius, std::move(profile)));
+}
+#include "glsl/GrGLSLFragmentProcessor.h"
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLProgramBuilder.h"
+#include "GrTexture.h"
+#include "SkSLCPP.h"
+#include "SkSLUtil.h"
+class GrGLSLCircleBlurFragmentProcessor : public GrGLSLFragmentProcessor {
+public:
+    GrGLSLCircleBlurFragmentProcessor() {}
+    void emitCode(EmitArgs& args) override {
+        GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+        const GrCircleBlurFragmentProcessor& _outer =
+                args.fFp.cast<GrCircleBlurFragmentProcessor>();
+        (void)_outer;
+        auto circleRect = _outer.circleRect();
+        (void)circleRect;
+        auto textureRadius = _outer.textureRadius();
+        (void)textureRadius;
+        auto solidRadius = _outer.solidRadius();
+        (void)solidRadius;
+        fCircleDataVar = args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kHalf4_GrSLType,
+                                                          kDefault_GrSLPrecision, "circleData");
+        fragBuilder->codeAppendf(
+                "half2 vec = half2(half((sk_FragCoord.x - float(%s.x)) * float(%s.w)), "
+                "half((sk_FragCoord.y - float(%s.y)) * float(%s.w)));\nhalf dist = "
+                "float(length(vec)) + (0.5 - float(%s.z)) * float(%s.w);\n%s = %s * texture(%s, "
+                "float2(half2(dist, 0.5))).%s.w;\n",
+                args.fUniformHandler->getUniformCStr(fCircleDataVar),
+                args.fUniformHandler->getUniformCStr(fCircleDataVar),
+                args.fUniformHandler->getUniformCStr(fCircleDataVar),
+                args.fUniformHandler->getUniformCStr(fCircleDataVar),
+                args.fUniformHandler->getUniformCStr(fCircleDataVar),
+                args.fUniformHandler->getUniformCStr(fCircleDataVar), args.fOutputColor,
+                args.fInputColor ? args.fInputColor : "half4(1)",
+                fragBuilder->getProgramBuilder()->samplerVariable(args.fTexSamplers[0]).c_str(),
+                fragBuilder->getProgramBuilder()->samplerSwizzle(args.fTexSamplers[0]).c_str());
+    }
+
+private:
+    void onSetData(const GrGLSLProgramDataManager& data,
+                   const GrFragmentProcessor& _proc) override {
+        const GrCircleBlurFragmentProcessor& _outer = _proc.cast<GrCircleBlurFragmentProcessor>();
+        auto circleRect = _outer.circleRect();
+        (void)circleRect;
+        auto textureRadius = _outer.textureRadius();
+        (void)textureRadius;
+        auto solidRadius = _outer.solidRadius();
+        (void)solidRadius;
+        GrSurfaceProxy& blurProfileSamplerProxy = *_outer.textureSampler(0).proxy();
+        GrTexture& blurProfileSampler = *blurProfileSamplerProxy.priv().peekTexture();
+        (void)blurProfileSampler;
+        UniformHandle& circleData = fCircleDataVar;
+        (void)circleData;
+
+        data.set4f(circleData, circleRect.centerX(), circleRect.centerY(), solidRadius,
+                   1.f / textureRadius);
+    }
+    UniformHandle fCircleDataVar;
+};
+GrGLSLFragmentProcessor* GrCircleBlurFragmentProcessor::onCreateGLSLInstance() const {
+    return new GrGLSLCircleBlurFragmentProcessor();
+}
+void GrCircleBlurFragmentProcessor::onGetGLSLProcessorKey(const GrShaderCaps& caps,
+                                                          GrProcessorKeyBuilder* b) const {}
+bool GrCircleBlurFragmentProcessor::onIsEqual(const GrFragmentProcessor& other) const {
+    const GrCircleBlurFragmentProcessor& that = other.cast<GrCircleBlurFragmentProcessor>();
+    (void)that;
+    if (fCircleRect != that.fCircleRect) return false;
+    if (fTextureRadius != that.fTextureRadius) return false;
+    if (fSolidRadius != that.fSolidRadius) return false;
+    if (fBlurProfileSampler != that.fBlurProfileSampler) return false;
+    return true;
+}
+GrCircleBlurFragmentProcessor::GrCircleBlurFragmentProcessor(
+        const GrCircleBlurFragmentProcessor& src)
+        : INHERITED(kGrCircleBlurFragmentProcessor_ClassID, src.optimizationFlags())
+        , fCircleRect(src.fCircleRect)
+        , fTextureRadius(src.fTextureRadius)
+        , fSolidRadius(src.fSolidRadius)
+        , fBlurProfileSampler(src.fBlurProfileSampler) {
+    this->addTextureSampler(&fBlurProfileSampler);
+}
+std::unique_ptr<GrFragmentProcessor> GrCircleBlurFragmentProcessor::clone() const {
+    return std::unique_ptr<GrFragmentProcessor>(new GrCircleBlurFragmentProcessor(*this));
+}
+GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrCircleBlurFragmentProcessor);
+#if GR_TEST_UTILS
+std::unique_ptr<GrFragmentProcessor> GrCircleBlurFragmentProcessor::TestCreate(
+        GrProcessorTestData* testData) {
+    SkScalar wh = testData->fRandom->nextRangeScalar(100.f, 1000.f);
+    SkScalar sigma = testData->fRandom->nextRangeF(1.f, 10.f);
+    SkRect circle = SkRect::MakeWH(wh, wh);
+    return GrCircleBlurFragmentProcessor::Make(testData->proxyProvider(), circle, sigma);
+}
+#endif
+#endif