src/effects/GrCircleBlurFragmentProcessor.cpp - skia - Git at Google

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "GrCircleBlurFragmentProcessor.h"

 #if SK_SUPPORT_GPU

 #include "GrContext.h"
 #include "GrInvariantOutput.h"
 #include "GrTextureProvider.h"

 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLFragmentShaderBuilder.h"
 #include "glsl/GrGLSLProgramDataManager.h"
 #include "glsl/GrGLSLUniformHandler.h"

 #include "SkFixed.h"

 class GrCircleBlurFragmentProcessor::GLSLProcessor : public GrGLSLFragmentProcessor {
 public:
     void emitCode(EmitArgs&) override;

 protected:
     void onSetData(const GrGLSLProgramDataManager&, const GrProcessor&) override;

 private:
     GrGLSLProgramDataManager::UniformHandle fDataUniform;

     typedef GrGLSLFragmentProcessor INHERITED;
 };

 void GrCircleBlurFragmentProcessor::GLSLProcessor::emitCode(EmitArgs& args) {
     const char *dataName;

     // The data is formatted as:
     // x,y  - the center of the circle
     // z    - inner radius that should map to 0th entry in the texture.
     // w    - the inverse of the distance over which the texture is stretched.
     fDataUniform = args.fUniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kVec4f_GrSLType,
                                                     kDefault_GrSLPrecision,
                                                     "data",
                                                     &dataName);

     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     const char *fragmentPos = fragBuilder->fragmentPosition();

     if (args.fInputColor) {
         fragBuilder->codeAppendf("vec4 src=%s;", args.fInputColor);
     } else {
         fragBuilder->codeAppendf("vec4 src=vec4(1);");
     }

     // We just want to compute "(length(vec) - %s.z + 0.5) * %s.w" but need to rearrange
     // for precision.
     fragBuilder->codeAppendf("vec2 vec = vec2( (%s.x - %s.x) * %s.w , (%s.y - %s.y) * %s.w );",
                              fragmentPos, dataName, dataName,
                              fragmentPos, dataName, dataName);
     fragBuilder->codeAppendf("float dist = length(vec) + (0.5 - %s.z) * %s.w;",
                              dataName, dataName);

     fragBuilder->codeAppendf("float intensity = ");
     fragBuilder->appendTextureLookup(args.fTexSamplers[0], "vec2(dist, 0.5)");
     fragBuilder->codeAppend(".a;");

     fragBuilder->codeAppendf("%s = src * intensity;\n", args.fOutputColor );
 }

 void GrCircleBlurFragmentProcessor::GLSLProcessor::onSetData(const GrGLSLProgramDataManager& pdman,
                                                              const GrProcessor& proc) {
     const GrCircleBlurFragmentProcessor& cbfp = proc.cast<GrCircleBlurFragmentProcessor>();
     const SkRect& circle = cbfp.fCircle;

     // The data is formatted as:
     // x,y  - the center of the circle
     // z    - inner radius that should map to 0th entry in the texture.
     // w    - the inverse of the distance over which the profile texture is stretched.
     pdman.set4f(fDataUniform, circle.centerX(), circle.centerY(), cbfp.fSolidRadius,
                 1.f / cbfp.fTextureRadius);
 }

 ///////////////////////////////////////////////////////////////////////////////

 GrCircleBlurFragmentProcessor::GrCircleBlurFragmentProcessor(const SkRect& circle,
                                                              float textureRadius,
                                                              float solidRadius,
                                                              GrTexture* blurProfile)
     : fCircle(circle)
     , fSolidRadius(solidRadius)
     , fTextureRadius(textureRadius)
     , fBlurProfileAccess(blurProfile, GrTextureParams::kBilerp_FilterMode) {
     this->initClassID<GrCircleBlurFragmentProcessor>();
     this->addTextureAccess(&fBlurProfileAccess);
     this->setWillReadFragmentPosition();
 }

 GrGLSLFragmentProcessor* GrCircleBlurFragmentProcessor::onCreateGLSLInstance() const {
     return new GLSLProcessor;
 }

 void GrCircleBlurFragmentProcessor::onGetGLSLProcessorKey(const GrGLSLCaps& caps,
                                                           GrProcessorKeyBuilder* b) const {
     // The code for this processor is always the same so there is nothing to add to the key.
     return;
 }

 void GrCircleBlurFragmentProcessor::onComputeInvariantOutput(GrInvariantOutput* inout) const {
     inout->mulByUnknownSingleComponent();
 }

 // 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 uint8_t* create_circle_profile(float sigma, float circleR, int profileTextureWidth) {
     const int numSteps = profileTextureWidth;
     uint8_t* weights = new uint8_t[numSteps];

     // 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;
     return weights;
 }

 static uint8_t* create_half_plane_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);
     uint8_t* profile = new uint8_t[profileWidth];

     // 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;
     return profile;
 }

 static GrTexture* create_profile_texture(GrTextureProvider* textureProvider, const SkRect& circle,
                                          float sigma, float* solidRadius, float* textureRadius) {
     float circleR = circle.width() / 2.0f;
     // 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();

     GrTexture *blurProfile = textureProvider->findAndRefTextureByUniqueKey(key);
     if (!blurProfile) {
         static constexpr int kProfileTextureWidth = 512;
         GrSurfaceDesc texDesc;
         texDesc.fWidth = kProfileTextureWidth;
         texDesc.fHeight = 1;
         texDesc.fConfig = kAlpha_8_GrPixelConfig;

         std::unique_ptr<uint8_t[]> profile(nullptr);
         if (useHalfPlaneApprox) {
             profile.reset(create_half_plane_profile(kProfileTextureWidth));
         } else {
             // Rescale params to the size of the texture we're creating.
             SkScalar scale = kProfileTextureWidth / *textureRadius;
             profile.reset(create_circle_profile(sigma * scale, circleR * scale,
                                                 kProfileTextureWidth));
         }

         blurProfile = textureProvider->createTexture(texDesc, SkBudgeted::kYes, profile.get(), 0);
         if (blurProfile) {
             textureProvider->assignUniqueKeyToTexture(key, blurProfile);
         }
     }

     return blurProfile;
 }

 //////////////////////////////////////////////////////////////////////////////

 sk_sp<GrFragmentProcessor> GrCircleBlurFragmentProcessor::Make(GrTextureProvider*textureProvider,
                                                                const SkRect& circle, float sigma) {
     float solidRadius;
     float textureRadius;
     sk_sp<GrTexture> profile(create_profile_texture(textureProvider, circle, sigma,
                                                     &solidRadius, &textureRadius));
     if (!profile) {
         return nullptr;
     }
     return sk_sp<GrFragmentProcessor>(
             new GrCircleBlurFragmentProcessor(circle, textureRadius, solidRadius, profile.get()));
 }

 //////////////////////////////////////////////////////////////////////////////

 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrCircleBlurFragmentProcessor);

 sk_sp<GrFragmentProcessor> GrCircleBlurFragmentProcessor::TestCreate(GrProcessorTestData* d) {
     SkScalar wh = d->fRandom->nextRangeScalar(100.f, 1000.f);
     SkScalar sigma = d->fRandom->nextRangeF(1.f,10.f);
     SkRect circle = SkRect::MakeWH(wh, wh);
     return GrCircleBlurFragmentProcessor::Make(d->fContext->textureProvider(), circle, sigma);
 }

 #endif
	/*
	* Copyright 2015 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "GrCircleBlurFragmentProcessor.h"

	#if SK_SUPPORT_GPU

	#include "GrContext.h"
	#include "GrInvariantOutput.h"
	#include "GrTextureProvider.h"

	#include "glsl/GrGLSLFragmentProcessor.h"
	#include "glsl/GrGLSLFragmentShaderBuilder.h"
	#include "glsl/GrGLSLProgramDataManager.h"
	#include "glsl/GrGLSLUniformHandler.h"

	#include "SkFixed.h"

	class GrCircleBlurFragmentProcessor::GLSLProcessor : public GrGLSLFragmentProcessor {
	public:
	void emitCode(EmitArgs&) override;

	protected:
	void onSetData(const GrGLSLProgramDataManager&, const GrProcessor&) override;

	private:
	GrGLSLProgramDataManager::UniformHandle fDataUniform;

	typedef GrGLSLFragmentProcessor INHERITED;
	};

	void GrCircleBlurFragmentProcessor::GLSLProcessor::emitCode(EmitArgs& args) {
	const char *dataName;

	// The data is formatted as:
	// x,y - the center of the circle
	// z - inner radius that should map to 0th entry in the texture.
	// w - the inverse of the distance over which the texture is stretched.
	fDataUniform = args.fUniformHandler->addUniform(kFragment_GrShaderFlag,
	kVec4f_GrSLType,
	kDefault_GrSLPrecision,
	"data",
	&dataName);

	GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
	const char *fragmentPos = fragBuilder->fragmentPosition();

	if (args.fInputColor) {
	fragBuilder->codeAppendf("vec4 src=%s;", args.fInputColor);
	} else {
	fragBuilder->codeAppendf("vec4 src=vec4(1);");
	}

	// We just want to compute "(length(vec) - %s.z + 0.5) * %s.w" but need to rearrange
	// for precision.
	fragBuilder->codeAppendf("vec2 vec = vec2( (%s.x - %s.x) * %s.w , (%s.y - %s.y) * %s.w );",
	fragmentPos, dataName, dataName,
	fragmentPos, dataName, dataName);
	fragBuilder->codeAppendf("float dist = length(vec) + (0.5 - %s.z) * %s.w;",
	dataName, dataName);

	fragBuilder->codeAppendf("float intensity = ");
	fragBuilder->appendTextureLookup(args.fTexSamplers[0], "vec2(dist, 0.5)");
	fragBuilder->codeAppend(".a;");

	fragBuilder->codeAppendf("%s = src * intensity;\n", args.fOutputColor );
	}

	void GrCircleBlurFragmentProcessor::GLSLProcessor::onSetData(const GrGLSLProgramDataManager& pdman,
	const GrProcessor& proc) {
	const GrCircleBlurFragmentProcessor& cbfp = proc.cast<GrCircleBlurFragmentProcessor>();
	const SkRect& circle = cbfp.fCircle;

	// The data is formatted as:
	// x,y - the center of the circle
	// z - inner radius that should map to 0th entry in the texture.
	// w - the inverse of the distance over which the profile texture is stretched.
	pdman.set4f(fDataUniform, circle.centerX(), circle.centerY(), cbfp.fSolidRadius,
	1.f / cbfp.fTextureRadius);
	}

	///////////////////////////////////////////////////////////////////////////////

	GrCircleBlurFragmentProcessor::GrCircleBlurFragmentProcessor(const SkRect& circle,
	float textureRadius,
	float solidRadius,
	GrTexture* blurProfile)
	: fCircle(circle)
	, fSolidRadius(solidRadius)
	, fTextureRadius(textureRadius)
	, fBlurProfileAccess(blurProfile, GrTextureParams::kBilerp_FilterMode) {
	this->initClassID<GrCircleBlurFragmentProcessor>();
	this->addTextureAccess(&fBlurProfileAccess);
	this->setWillReadFragmentPosition();
	}

	GrGLSLFragmentProcessor* GrCircleBlurFragmentProcessor::onCreateGLSLInstance() const {
	return new GLSLProcessor;
	}

	void GrCircleBlurFragmentProcessor::onGetGLSLProcessorKey(const GrGLSLCaps& caps,
	GrProcessorKeyBuilder* b) const {
	// The code for this processor is always the same so there is nothing to add to the key.
	return;
	}

	void GrCircleBlurFragmentProcessor::onComputeInvariantOutput(GrInvariantOutput* inout) const {
	inout->mulByUnknownSingleComponent();
	}

	// 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 uint8_t* create_circle_profile(float sigma, float circleR, int profileTextureWidth) {
	const int numSteps = profileTextureWidth;
	uint8_t* weights = new uint8_t[numSteps];

	// 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;
	return weights;
	}

	static uint8_t* create_half_plane_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);
	uint8_t* profile = new uint8_t[profileWidth];

	// 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;
	return profile;
	}

	static GrTexture* create_profile_texture(GrTextureProvider* textureProvider, const SkRect& circle,
	float sigma, float* solidRadius, float* textureRadius) {
	float circleR = circle.width() / 2.0f;
	// 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();

	GrTexture *blurProfile = textureProvider->findAndRefTextureByUniqueKey(key);
	if (!blurProfile) {
	static constexpr int kProfileTextureWidth = 512;
	GrSurfaceDesc texDesc;
	texDesc.fWidth = kProfileTextureWidth;
	texDesc.fHeight = 1;
	texDesc.fConfig = kAlpha_8_GrPixelConfig;

	std::unique_ptr<uint8_t[]> profile(nullptr);
	if (useHalfPlaneApprox) {
	profile.reset(create_half_plane_profile(kProfileTextureWidth));
	} else {
	// Rescale params to the size of the texture we're creating.
	SkScalar scale = kProfileTextureWidth / *textureRadius;
	profile.reset(create_circle_profile(sigma * scale, circleR * scale,
	kProfileTextureWidth));
	}

	blurProfile = textureProvider->createTexture(texDesc, SkBudgeted::kYes, profile.get(), 0);
	if (blurProfile) {
	textureProvider->assignUniqueKeyToTexture(key, blurProfile);
	}
	}

	return blurProfile;
	}

	//////////////////////////////////////////////////////////////////////////////

	sk_sp<GrFragmentProcessor> GrCircleBlurFragmentProcessor::Make(GrTextureProvider*textureProvider,
	const SkRect& circle, float sigma) {
	float solidRadius;
	float textureRadius;
	sk_sp<GrTexture> profile(create_profile_texture(textureProvider, circle, sigma,
	&solidRadius, &textureRadius));
	if (!profile) {
	return nullptr;
	}
	return sk_sp<GrFragmentProcessor>(
	new GrCircleBlurFragmentProcessor(circle, textureRadius, solidRadius, profile.get()));
	}

	//////////////////////////////////////////////////////////////////////////////

	GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrCircleBlurFragmentProcessor);

	sk_sp<GrFragmentProcessor> GrCircleBlurFragmentProcessor::TestCreate(GrProcessorTestData* d) {
	SkScalar wh = d->fRandom->nextRangeScalar(100.f, 1000.f);
	SkScalar sigma = d->fRandom->nextRangeF(1.f,10.f);
	SkRect circle = SkRect::MakeWH(wh, wh);
	return GrCircleBlurFragmentProcessor::Make(d->fContext->textureProvider(), circle, sigma);
	}

	#endif