src/third_party/skia/src/core/SkRasterPipelineBlitter.cpp - cobalt - Git at Google

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "SkArenaAlloc.h"
 #include "SkBlitter.h"
 #include "SkBlendModePriv.h"
 #include "SkColor.h"
 #include "SkColorFilter.h"
 #include "SkColorSpaceXformer.h"
 #include "SkOpts.h"
 #include "SkPM4f.h"
 #include "SkPM4fPriv.h"
 #include "SkRasterPipeline.h"
 #include "SkShader.h"
 #include "SkShaderBase.h"
 #include "SkUtils.h"
 #include "../jumper/SkJumper.h"

 class SkRasterPipelineBlitter final : public SkBlitter {
 public:
     // This is our common entrypoint for creating the blitter once we've sorted out shaders.
     static SkBlitter* Create(const SkPixmap&, const SkPaint&, SkArenaAlloc*,
                              const SkRasterPipeline& shaderPipeline,
                              SkShaderBase::Context*,
                              bool is_opaque, bool is_constant);

     SkRasterPipelineBlitter(SkPixmap dst,
                             SkBlendMode blend,
                             SkArenaAlloc* alloc,
                             SkShaderBase::Context* burstCtx)
         : fDst(dst)
         , fBlend(blend)
         , fAlloc(alloc)
         , fBurstCtx(burstCtx)
         , fColorPipeline(alloc)
     {}

     void blitH     (int x, int y, int w)                            override;
     void blitAntiH (int x, int y, const SkAlpha[], const int16_t[]) override;
     void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1)               override;
     void blitMask  (const SkMask&, const SkIRect& clip)             override;

     // TODO: The default implementations of the other blits look fine,
     // but some of them like blitV could probably benefit from custom
     // blits using something like a SkRasterPipeline::runFew() method.

 private:
     void append_load_d(SkRasterPipeline*) const;
     void append_blend (SkRasterPipeline*) const;
     void maybe_clamp  (SkRasterPipeline*) const;
     void append_store (SkRasterPipeline*) const;

     // If we have an burst context, use it to fill our shader buffer.
     void maybe_shade(int x, int y, int w);

     SkPixmap               fDst;
     SkBlendMode            fBlend;
     SkArenaAlloc*          fAlloc;
     SkShaderBase::Context* fBurstCtx;
     SkRasterPipeline       fColorPipeline;

     // We may be able to specialize blitH() into a memset.
     bool     fCanMemsetInBlitH = false;
     uint64_t fMemsetColor      = 0;     // Big enough for largest dst format, F16.

     // Built lazily on first use.
     std::function<void(size_t, size_t, size_t)> fBlitH,
                                                 fBlitAntiH,
                                                 fBlitMaskA8,
                                                 fBlitMaskLCD16;

     // These values are pointed to by the blit pipelines above,
     // which allows us to adjust them from call to call.
     void*              fShaderOutput    = nullptr;
     void*              fDstPtr          = nullptr;
     const void*        fMaskPtr         = nullptr;
     float              fCurrentCoverage = 0.0f;
     float              fDitherRate      = 0.0f;

     std::vector<SkPM4f> fShaderBuffer;

     typedef SkBlitter INHERITED;
 };

 SkBlitter* SkCreateRasterPipelineBlitter(const SkPixmap& dst,
                                          const SkPaint& paint,
                                          const SkMatrix& ctm,
                                          SkArenaAlloc* alloc) {
     SkColorSpace* dstCS = dst.colorSpace();
     SkPM4f paintColor = SkPM4f_from_SkColor(paint.getColor(), dstCS);
     auto shader = as_SB(paint.getShader());

     SkRasterPipeline_<256> shaderPipeline;
     if (!shader) {
         // Having no shader makes things nice and easy... just use the paint color.
         shaderPipeline.append_uniform_color(alloc, paintColor);
         bool is_opaque    = paintColor.a() == 1.0f,
              is_constant  = true;
         return SkRasterPipelineBlitter::Create(dst, paint, alloc,
                                                shaderPipeline, nullptr,
                                                is_opaque, is_constant);
     }

     bool is_opaque    = shader->isOpaque() && paintColor.a() == 1.0f;
     bool is_constant  = shader->isConstant();

     // Check whether the shader prefers to run in burst mode.
     if (auto* burstCtx = shader->makeBurstPipelineContext(
         SkShaderBase::ContextRec(paint, ctm, nullptr, SkShaderBase::ContextRec::kPM4f_DstType,
                                  dstCS), alloc)) {
         return SkRasterPipelineBlitter::Create(dst, paint, alloc,
                                                shaderPipeline, burstCtx,
                                                is_opaque, is_constant);
     }

     if (shader->appendStages(&shaderPipeline, dstCS, alloc, ctm, paint)) {
         if (paintColor.a() != 1.0f) {
             shaderPipeline.append(SkRasterPipeline::scale_1_float,
                                   alloc->make<float>(paintColor.a()));
         }
         return SkRasterPipelineBlitter::Create(dst, paint, alloc, shaderPipeline, nullptr,
                                                is_opaque, is_constant);
     }

     // The shader has opted out of drawing anything.
     return alloc->make<SkNullBlitter>();
 }

 SkBlitter* SkCreateRasterPipelineBlitter(const SkPixmap& dst,
                                          const SkPaint& paint,
                                          const SkRasterPipeline& shaderPipeline,
                                          bool is_opaque,
                                          SkArenaAlloc* alloc) {
     bool is_constant = false;  // If this were the case, it'd be better to just set a paint color.
     return SkRasterPipelineBlitter::Create(dst, paint, alloc, shaderPipeline, nullptr,
                                            is_opaque, is_constant);
 }

 SkBlitter* SkRasterPipelineBlitter::Create(const SkPixmap& dst,
                                            const SkPaint& paint,
                                            SkArenaAlloc* alloc,
                                            const SkRasterPipeline& shaderPipeline,
                                            SkShaderBase::Context* burstCtx,
                                            bool is_opaque,
                                            bool is_constant) {
     auto blitter = alloc->make<SkRasterPipelineBlitter>(dst,
                                                         paint.getBlendMode(),
                                                         alloc,
                                                         burstCtx);

     // Our job in this factory is to fill out the blitter's color pipeline.
     // This is the common front of the full blit pipelines, each constructed lazily on first use.
     // The full blit pipelines handle reading and writing the dst, blending, coverage, dithering.
     auto colorPipeline = &blitter->fColorPipeline;

     // Let's get the shader in first.
     if (burstCtx) {
         colorPipeline->append(SkRasterPipeline::load_f32, &blitter->fShaderOutput);
     } else {
         colorPipeline->extend(shaderPipeline);
     }

     // If there's a color filter it comes next.
     if (auto colorFilter = paint.getColorFilter()) {
         colorFilter->appendStages(colorPipeline, dst.colorSpace(), alloc, is_opaque);
         is_opaque = is_opaque && (colorFilter->getFlags() & SkColorFilter::kAlphaUnchanged_Flag);
     }

     // Not all formats make sense to dither (think, F16).  We set their dither rate to zero.
     // We need to decide if we're going to dither now to keep is_constant accurate.
     if (paint.isDither()) {
         switch (dst.info().colorType()) {
             default:                     blitter->fDitherRate =     0.0f; break;
             case kARGB_4444_SkColorType: blitter->fDitherRate =  1/15.0f; break;
             case   kRGB_565_SkColorType: blitter->fDitherRate =  1/63.0f; break;
             case    kGray_8_SkColorType:
             case kRGBA_8888_SkColorType:
             case kBGRA_8888_SkColorType: blitter->fDitherRate = 1/255.0f; break;
         }
         // TODO: for constant colors, we could try to measure the effect of dithering, and if
         //       it has no value (i.e. all variations result in the same 32bit color, then we
         //       could disable it (for speed, by not adding the stage).
     }
     is_constant = is_constant && (blitter->fDitherRate == 0.0f);

     // We're logically done here.  The code between here and return blitter is all optimization.

     // A pipeline that's still constant here can collapse back into a constant color.
     if (is_constant) {
         SkPM4f storage;
         SkPM4f* constantColor = &storage;
         colorPipeline->append(SkRasterPipeline::store_f32, &constantColor);
         colorPipeline->run(0,0,1);
         colorPipeline->reset();
         colorPipeline->append_uniform_color(alloc, *constantColor);

         is_opaque = constantColor->a() == 1.0f;
     }

     // We can strength-reduce SrcOver into Src when opaque.
     if (is_opaque && blitter->fBlend == SkBlendMode::kSrcOver) {
         blitter->fBlend = SkBlendMode::kSrc;
     }

     // When we're drawing a constant color in Src mode, we can sometimes just memset.
     // (The previous two optimizations help find more opportunities for this one.)
     if (is_constant && blitter->fBlend == SkBlendMode::kSrc) {
         // Run our color pipeline all the way through to produce what we'd memset when we can.
         // Not all blits can memset, so we need to keep colorPipeline too.
         SkRasterPipeline_<256> p;
         p.extend(*colorPipeline);
         blitter->fDstPtr = &blitter->fMemsetColor;
         blitter->append_store(&p);
         p.run(0,0,1);

         blitter->fCanMemsetInBlitH = true;
     }

     return blitter;
 }

 void SkRasterPipelineBlitter::append_load_d(SkRasterPipeline* p) const {
     switch (fDst.info().colorType()) {
         case kGray_8_SkColorType:    p->append(SkRasterPipeline::load_g8_dst,   &fDstPtr); break;
         case kAlpha_8_SkColorType:   p->append(SkRasterPipeline::load_a8_dst,   &fDstPtr); break;
         case kRGB_565_SkColorType:   p->append(SkRasterPipeline::load_565_dst,  &fDstPtr); break;
         case kARGB_4444_SkColorType: p->append(SkRasterPipeline::load_4444_dst, &fDstPtr); break;
         case kBGRA_8888_SkColorType: p->append(SkRasterPipeline::load_bgra_dst, &fDstPtr); break;
         case kRGBA_8888_SkColorType: p->append(SkRasterPipeline::load_8888_dst, &fDstPtr); break;
         case kRGBA_F16_SkColorType:  p->append(SkRasterPipeline::load_f16_dst,  &fDstPtr); break;
         default:                                                                           break;
     }
     if (fDst.info().gammaCloseToSRGB()) {
         p->append_from_srgb_dst(fDst.info().alphaType());
     }
 }

 void SkRasterPipelineBlitter::append_store(SkRasterPipeline* p) const {
     if (fDst.info().gammaCloseToSRGB()) {
         p->append(SkRasterPipeline::to_srgb);
     }
     if (fDitherRate > 0.0f) {
         // We dither after any sRGB transfer function to make sure our 1/255.0f is sensible
         // over the whole range.  If we did it before, 1/255.0f is too big a rate near zero.
         p->append(SkRasterPipeline::dither, &fDitherRate);
     }

     switch (fDst.info().colorType()) {
         case kGray_8_SkColorType:    p->append(SkRasterPipeline::luminance_to_alpha); // fallthru
         case kAlpha_8_SkColorType:   p->append(SkRasterPipeline::store_a8,   &fDstPtr); break;
         case kRGB_565_SkColorType:   p->append(SkRasterPipeline::store_565,  &fDstPtr); break;
         case kARGB_4444_SkColorType: p->append(SkRasterPipeline::store_4444, &fDstPtr); break;
         case kBGRA_8888_SkColorType: p->append(SkRasterPipeline::store_bgra, &fDstPtr); break;
         case kRGBA_8888_SkColorType: p->append(SkRasterPipeline::store_8888, &fDstPtr); break;
         case kRGBA_F16_SkColorType:  p->append(SkRasterPipeline::store_f16,  &fDstPtr); break;
         default: break;
     }
 }

 void SkRasterPipelineBlitter::append_blend(SkRasterPipeline* p) const {
     if (fDst.info().alphaType() == kUnpremul_SkAlphaType) {
         p->append(SkRasterPipeline::premul_dst);
     }
     SkBlendMode_AppendStagesNoClamp(fBlend, p);
     if (fDst.info().alphaType() == kUnpremul_SkAlphaType) {
         p->append(SkRasterPipeline::unpremul);
     }
 }

 void SkRasterPipelineBlitter::maybe_clamp(SkRasterPipeline* p) const {
     SkBlendMode_AppendClampIfNeeded(fBlend, p);
 }

 void SkRasterPipelineBlitter::maybe_shade(int x, int y, int w) {
     if (fBurstCtx) {
         if (w > SkToInt(fShaderBuffer.size())) {
             fShaderBuffer.resize(w);
         }
         fBurstCtx->shadeSpan4f(x,y, fShaderBuffer.data(), w);
         // We'll be reading from fShaderOutput + x.
         fShaderOutput = fShaderBuffer.data() - x;
     }
 }

 void SkRasterPipelineBlitter::blitH(int x, int y, int w) {
     fDstPtr = fDst.writable_addr(0,y);

     if (fCanMemsetInBlitH) {
         switch (fDst.shiftPerPixel()) {
             case 0:    memset  ((uint8_t *)fDstPtr + x, fMemsetColor, w); return;
             case 1: sk_memset16((uint16_t*)fDstPtr + x, fMemsetColor, w); return;
             case 2: sk_memset32((uint32_t*)fDstPtr + x, fMemsetColor, w); return;
             case 3: sk_memset64((uint64_t*)fDstPtr + x, fMemsetColor, w); return;
             default: break;
         }
     }

     if (!fBlitH) {
         SkRasterPipeline p(fAlloc);
         p.extend(fColorPipeline);
         if (fBlend == SkBlendMode::kSrcOver
                 && fDst.info().colorType() == kRGBA_8888_SkColorType
                 && !fDst.colorSpace()
                 && fDst.info().alphaType() != kUnpremul_SkAlphaType
                 && fDitherRate == 0.0f) {
             p.append(SkRasterPipeline::srcover_rgba_8888, &fDstPtr);
         } else {
             if (fBlend != SkBlendMode::kSrc) {
                 this->append_load_d(&p);
                 this->append_blend(&p);
                 this->maybe_clamp(&p);
             }
             this->append_store(&p);
         }
         fBlitH = p.compile();
     }
     this->maybe_shade(x,y,w);
     fBlitH(x,y,w);
 }

 void SkRasterPipelineBlitter::blitAntiH(int x, int y, const SkAlpha aa[], const int16_t runs[]) {
     if (!fBlitAntiH) {
         SkRasterPipeline p(fAlloc);
         p.extend(fColorPipeline);
         if (fBlend == SkBlendMode::kSrcOver) {
             p.append(SkRasterPipeline::scale_1_float, &fCurrentCoverage);
             this->append_load_d(&p);
             this->append_blend(&p);
         } else {
             this->append_load_d(&p);
             this->append_blend(&p);
             p.append(SkRasterPipeline::lerp_1_float, &fCurrentCoverage);
         }
         this->maybe_clamp(&p);
         this->append_store(&p);
         fBlitAntiH = p.compile();
     }

     fDstPtr = fDst.writable_addr(0,y);
     for (int16_t run = *runs; run > 0; run = *runs) {
         switch (*aa) {
             case 0x00:                       break;
             case 0xff: this->blitH(x,y,run); break;
             default:
                 this->maybe_shade(x,y,run);
                 fCurrentCoverage = *aa * (1/255.0f);
                 fBlitAntiH(x,y,run);
         }
         x    += run;
         runs += run;
         aa   += run;
     }
 }

 void SkRasterPipelineBlitter::blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) {
     SkIRect clip = {x,y, x+2,y+1};
     uint8_t coverage[] = { (uint8_t)a0, (uint8_t)a1 };

     SkMask mask;
     mask.fImage    = coverage;
     mask.fBounds   = clip;
     mask.fRowBytes = 2;
     mask.fFormat   = SkMask::kA8_Format;

     this->blitMask(mask, clip);
 }

 void SkRasterPipelineBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
     if (mask.fFormat == SkMask::kBW_Format) {
         // TODO: native BW masks?
         return INHERITED::blitMask(mask, clip);
     }

     if (mask.fFormat == SkMask::kA8_Format && !fBlitMaskA8) {
         SkRasterPipeline p(fAlloc);
         p.extend(fColorPipeline);
         if (fBlend == SkBlendMode::kSrcOver) {
             p.append(SkRasterPipeline::scale_u8, &fMaskPtr);
             this->append_load_d(&p);
             this->append_blend(&p);
         } else {
             this->append_load_d(&p);
             this->append_blend(&p);
             p.append(SkRasterPipeline::lerp_u8, &fMaskPtr);
         }
         this->maybe_clamp(&p);
         this->append_store(&p);
         fBlitMaskA8 = p.compile();
     }

     if (mask.fFormat == SkMask::kLCD16_Format && !fBlitMaskLCD16) {
         SkRasterPipeline p(fAlloc);
         p.extend(fColorPipeline);
         this->append_load_d(&p);
         this->append_blend(&p);
         p.append(SkRasterPipeline::lerp_565, &fMaskPtr);
         this->maybe_clamp(&p);
         this->append_store(&p);
         fBlitMaskLCD16 = p.compile();
     }

     int x = clip.left();
     for (int y = clip.top(); y < clip.bottom(); y++) {
         fDstPtr = fDst.writable_addr(0,y);

         this->maybe_shade(x,y,clip.width());
         switch (mask.fFormat) {
             case SkMask::kA8_Format:
                 fMaskPtr = mask.getAddr8(x,y)-x;
                 fBlitMaskA8(x,y,clip.width());
                 break;
             case SkMask::kLCD16_Format:
                 fMaskPtr = mask.getAddrLCD16(x,y)-x;
                 fBlitMaskLCD16(x,y,clip.width());
                 break;
             default:
                 // TODO
                 break;
         }
     }
 }
	/*
	* Copyright 2016 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "SkArenaAlloc.h"
	#include "SkBlitter.h"
	#include "SkBlendModePriv.h"
	#include "SkColor.h"
	#include "SkColorFilter.h"
	#include "SkColorSpaceXformer.h"
	#include "SkOpts.h"
	#include "SkPM4f.h"
	#include "SkPM4fPriv.h"
	#include "SkRasterPipeline.h"
	#include "SkShader.h"
	#include "SkShaderBase.h"
	#include "SkUtils.h"
	#include "../jumper/SkJumper.h"

	class SkRasterPipelineBlitter final : public SkBlitter {
	public:
	// This is our common entrypoint for creating the blitter once we've sorted out shaders.
	static SkBlitter* Create(const SkPixmap&, const SkPaint&, SkArenaAlloc*,
	const SkRasterPipeline& shaderPipeline,
	SkShaderBase::Context*,
	bool is_opaque, bool is_constant);

	SkRasterPipelineBlitter(SkPixmap dst,
	SkBlendMode blend,
	SkArenaAlloc* alloc,
	SkShaderBase::Context* burstCtx)
	: fDst(dst)
	, fBlend(blend)
	, fAlloc(alloc)
	, fBurstCtx(burstCtx)
	, fColorPipeline(alloc)
	{}

	void blitH (int x, int y, int w) override;
	void blitAntiH (int x, int y, const SkAlpha[], const int16_t[]) override;
	void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) override;
	void blitMask (const SkMask&, const SkIRect& clip) override;

	// TODO: The default implementations of the other blits look fine,
	// but some of them like blitV could probably benefit from custom
	// blits using something like a SkRasterPipeline::runFew() method.

	private:
	void append_load_d(SkRasterPipeline*) const;
	void append_blend (SkRasterPipeline*) const;
	void maybe_clamp (SkRasterPipeline*) const;
	void append_store (SkRasterPipeline*) const;

	// If we have an burst context, use it to fill our shader buffer.
	void maybe_shade(int x, int y, int w);

	SkPixmap fDst;
	SkBlendMode fBlend;
	SkArenaAlloc* fAlloc;
	SkShaderBase::Context* fBurstCtx;
	SkRasterPipeline fColorPipeline;

	// We may be able to specialize blitH() into a memset.
	bool fCanMemsetInBlitH = false;
	uint64_t fMemsetColor = 0; // Big enough for largest dst format, F16.

	// Built lazily on first use.
	std::function<void(size_t, size_t, size_t)> fBlitH,
	fBlitAntiH,
	fBlitMaskA8,
	fBlitMaskLCD16;

	// These values are pointed to by the blit pipelines above,
	// which allows us to adjust them from call to call.
	void* fShaderOutput = nullptr;
	void* fDstPtr = nullptr;
	const void* fMaskPtr = nullptr;
	float fCurrentCoverage = 0.0f;
	float fDitherRate = 0.0f;

	std::vector<SkPM4f> fShaderBuffer;

	typedef SkBlitter INHERITED;
	};

	SkBlitter* SkCreateRasterPipelineBlitter(const SkPixmap& dst,
	const SkPaint& paint,
	const SkMatrix& ctm,
	SkArenaAlloc* alloc) {
	SkColorSpace* dstCS = dst.colorSpace();
	SkPM4f paintColor = SkPM4f_from_SkColor(paint.getColor(), dstCS);
	auto shader = as_SB(paint.getShader());

	SkRasterPipeline_<256> shaderPipeline;
	if (!shader) {
	// Having no shader makes things nice and easy... just use the paint color.
	shaderPipeline.append_uniform_color(alloc, paintColor);
	bool is_opaque = paintColor.a() == 1.0f,
	is_constant = true;
	return SkRasterPipelineBlitter::Create(dst, paint, alloc,
	shaderPipeline, nullptr,
	is_opaque, is_constant);
	}

	bool is_opaque = shader->isOpaque() && paintColor.a() == 1.0f;
	bool is_constant = shader->isConstant();

	// Check whether the shader prefers to run in burst mode.
	if (auto* burstCtx = shader->makeBurstPipelineContext(
	SkShaderBase::ContextRec(paint, ctm, nullptr, SkShaderBase::ContextRec::kPM4f_DstType,
	dstCS), alloc)) {
	return SkRasterPipelineBlitter::Create(dst, paint, alloc,
	shaderPipeline, burstCtx,
	is_opaque, is_constant);
	}

	if (shader->appendStages(&shaderPipeline, dstCS, alloc, ctm, paint)) {
	if (paintColor.a() != 1.0f) {
	shaderPipeline.append(SkRasterPipeline::scale_1_float,
	alloc->make<float>(paintColor.a()));
	}
	return SkRasterPipelineBlitter::Create(dst, paint, alloc, shaderPipeline, nullptr,
	is_opaque, is_constant);
	}

	// The shader has opted out of drawing anything.
	return alloc->make<SkNullBlitter>();
	}

	SkBlitter* SkCreateRasterPipelineBlitter(const SkPixmap& dst,
	const SkPaint& paint,
	const SkRasterPipeline& shaderPipeline,
	bool is_opaque,
	SkArenaAlloc* alloc) {
	bool is_constant = false; // If this were the case, it'd be better to just set a paint color.
	return SkRasterPipelineBlitter::Create(dst, paint, alloc, shaderPipeline, nullptr,
	is_opaque, is_constant);
	}

	SkBlitter* SkRasterPipelineBlitter::Create(const SkPixmap& dst,
	const SkPaint& paint,
	SkArenaAlloc* alloc,
	const SkRasterPipeline& shaderPipeline,
	SkShaderBase::Context* burstCtx,
	bool is_opaque,
	bool is_constant) {
	auto blitter = alloc->make<SkRasterPipelineBlitter>(dst,
	paint.getBlendMode(),
	alloc,
	burstCtx);

	// Our job in this factory is to fill out the blitter's color pipeline.
	// This is the common front of the full blit pipelines, each constructed lazily on first use.
	// The full blit pipelines handle reading and writing the dst, blending, coverage, dithering.
	auto colorPipeline = &blitter->fColorPipeline;

	// Let's get the shader in first.
	if (burstCtx) {
	colorPipeline->append(SkRasterPipeline::load_f32, &blitter->fShaderOutput);
	} else {
	colorPipeline->extend(shaderPipeline);
	}

	// If there's a color filter it comes next.
	if (auto colorFilter = paint.getColorFilter()) {
	colorFilter->appendStages(colorPipeline, dst.colorSpace(), alloc, is_opaque);
	is_opaque = is_opaque && (colorFilter->getFlags() & SkColorFilter::kAlphaUnchanged_Flag);
	}

	// Not all formats make sense to dither (think, F16). We set their dither rate to zero.
	// We need to decide if we're going to dither now to keep is_constant accurate.
	if (paint.isDither()) {
	switch (dst.info().colorType()) {
	default: blitter->fDitherRate = 0.0f; break;
	case kARGB_4444_SkColorType: blitter->fDitherRate = 1/15.0f; break;
	case kRGB_565_SkColorType: blitter->fDitherRate = 1/63.0f; break;
	case kGray_8_SkColorType:
	case kRGBA_8888_SkColorType:
	case kBGRA_8888_SkColorType: blitter->fDitherRate = 1/255.0f; break;
	}
	// TODO: for constant colors, we could try to measure the effect of dithering, and if
	// it has no value (i.e. all variations result in the same 32bit color, then we
	// could disable it (for speed, by not adding the stage).
	}
	is_constant = is_constant && (blitter->fDitherRate == 0.0f);

	// We're logically done here. The code between here and return blitter is all optimization.

	// A pipeline that's still constant here can collapse back into a constant color.
	if (is_constant) {
	SkPM4f storage;
	SkPM4f* constantColor = &storage;
	colorPipeline->append(SkRasterPipeline::store_f32, &constantColor);
	colorPipeline->run(0,0,1);
	colorPipeline->reset();
	colorPipeline->append_uniform_color(alloc, *constantColor);

	is_opaque = constantColor->a() == 1.0f;
	}

	// We can strength-reduce SrcOver into Src when opaque.
	if (is_opaque && blitter->fBlend == SkBlendMode::kSrcOver) {
	blitter->fBlend = SkBlendMode::kSrc;
	}

	// When we're drawing a constant color in Src mode, we can sometimes just memset.
	// (The previous two optimizations help find more opportunities for this one.)
	if (is_constant && blitter->fBlend == SkBlendMode::kSrc) {
	// Run our color pipeline all the way through to produce what we'd memset when we can.
	// Not all blits can memset, so we need to keep colorPipeline too.
	SkRasterPipeline_<256> p;
	p.extend(*colorPipeline);
	blitter->fDstPtr = &blitter->fMemsetColor;
	blitter->append_store(&p);
	p.run(0,0,1);

	blitter->fCanMemsetInBlitH = true;
	}

	return blitter;
	}

	void SkRasterPipelineBlitter::append_load_d(SkRasterPipeline* p) const {
	switch (fDst.info().colorType()) {
	case kGray_8_SkColorType: p->append(SkRasterPipeline::load_g8_dst, &fDstPtr); break;
	case kAlpha_8_SkColorType: p->append(SkRasterPipeline::load_a8_dst, &fDstPtr); break;
	case kRGB_565_SkColorType: p->append(SkRasterPipeline::load_565_dst, &fDstPtr); break;
	case kARGB_4444_SkColorType: p->append(SkRasterPipeline::load_4444_dst, &fDstPtr); break;
	case kBGRA_8888_SkColorType: p->append(SkRasterPipeline::load_bgra_dst, &fDstPtr); break;
	case kRGBA_8888_SkColorType: p->append(SkRasterPipeline::load_8888_dst, &fDstPtr); break;
	case kRGBA_F16_SkColorType: p->append(SkRasterPipeline::load_f16_dst, &fDstPtr); break;
	default: break;
	}
	if (fDst.info().gammaCloseToSRGB()) {
	p->append_from_srgb_dst(fDst.info().alphaType());
	}
	}

	void SkRasterPipelineBlitter::append_store(SkRasterPipeline* p) const {
	if (fDst.info().gammaCloseToSRGB()) {
	p->append(SkRasterPipeline::to_srgb);
	}
	if (fDitherRate > 0.0f) {
	// We dither after any sRGB transfer function to make sure our 1/255.0f is sensible
	// over the whole range. If we did it before, 1/255.0f is too big a rate near zero.
	p->append(SkRasterPipeline::dither, &fDitherRate);
	}

	switch (fDst.info().colorType()) {
	case kGray_8_SkColorType: p->append(SkRasterPipeline::luminance_to_alpha); // fallthru
	case kAlpha_8_SkColorType: p->append(SkRasterPipeline::store_a8, &fDstPtr); break;
	case kRGB_565_SkColorType: p->append(SkRasterPipeline::store_565, &fDstPtr); break;
	case kARGB_4444_SkColorType: p->append(SkRasterPipeline::store_4444, &fDstPtr); break;
	case kBGRA_8888_SkColorType: p->append(SkRasterPipeline::store_bgra, &fDstPtr); break;
	case kRGBA_8888_SkColorType: p->append(SkRasterPipeline::store_8888, &fDstPtr); break;
	case kRGBA_F16_SkColorType: p->append(SkRasterPipeline::store_f16, &fDstPtr); break;
	default: break;
	}
	}

	void SkRasterPipelineBlitter::append_blend(SkRasterPipeline* p) const {
	if (fDst.info().alphaType() == kUnpremul_SkAlphaType) {
	p->append(SkRasterPipeline::premul_dst);
	}
	SkBlendMode_AppendStagesNoClamp(fBlend, p);
	if (fDst.info().alphaType() == kUnpremul_SkAlphaType) {
	p->append(SkRasterPipeline::unpremul);
	}
	}

	void SkRasterPipelineBlitter::maybe_clamp(SkRasterPipeline* p) const {
	SkBlendMode_AppendClampIfNeeded(fBlend, p);
	}

	void SkRasterPipelineBlitter::maybe_shade(int x, int y, int w) {
	if (fBurstCtx) {
	if (w > SkToInt(fShaderBuffer.size())) {
	fShaderBuffer.resize(w);
	}
	fBurstCtx->shadeSpan4f(x,y, fShaderBuffer.data(), w);
	// We'll be reading from fShaderOutput + x.
	fShaderOutput = fShaderBuffer.data() - x;
	}
	}

	void SkRasterPipelineBlitter::blitH(int x, int y, int w) {
	fDstPtr = fDst.writable_addr(0,y);

	if (fCanMemsetInBlitH) {
	switch (fDst.shiftPerPixel()) {
	case 0: memset ((uint8_t *)fDstPtr + x, fMemsetColor, w); return;
	case 1: sk_memset16((uint16_t*)fDstPtr + x, fMemsetColor, w); return;
	case 2: sk_memset32((uint32_t*)fDstPtr + x, fMemsetColor, w); return;
	case 3: sk_memset64((uint64_t*)fDstPtr + x, fMemsetColor, w); return;
	default: break;
	}
	}

	if (!fBlitH) {
	SkRasterPipeline p(fAlloc);
	p.extend(fColorPipeline);
	if (fBlend == SkBlendMode::kSrcOver
	&& fDst.info().colorType() == kRGBA_8888_SkColorType
	&& !fDst.colorSpace()
	&& fDst.info().alphaType() != kUnpremul_SkAlphaType
	&& fDitherRate == 0.0f) {
	p.append(SkRasterPipeline::srcover_rgba_8888, &fDstPtr);
	} else {
	if (fBlend != SkBlendMode::kSrc) {
	this->append_load_d(&p);
	this->append_blend(&p);
	this->maybe_clamp(&p);
	}
	this->append_store(&p);
	}
	fBlitH = p.compile();
	}
	this->maybe_shade(x,y,w);
	fBlitH(x,y,w);
	}

	void SkRasterPipelineBlitter::blitAntiH(int x, int y, const SkAlpha aa[], const int16_t runs[]) {
	if (!fBlitAntiH) {
	SkRasterPipeline p(fAlloc);
	p.extend(fColorPipeline);
	if (fBlend == SkBlendMode::kSrcOver) {
	p.append(SkRasterPipeline::scale_1_float, &fCurrentCoverage);
	this->append_load_d(&p);
	this->append_blend(&p);
	} else {
	this->append_load_d(&p);
	this->append_blend(&p);
	p.append(SkRasterPipeline::lerp_1_float, &fCurrentCoverage);
	}
	this->maybe_clamp(&p);
	this->append_store(&p);
	fBlitAntiH = p.compile();
	}

	fDstPtr = fDst.writable_addr(0,y);
	for (int16_t run = runs; run > 0; run = runs) {
	switch (*aa) {
	case 0x00: break;
	case 0xff: this->blitH(x,y,run); break;
	default:
	this->maybe_shade(x,y,run);
	fCurrentCoverage = aa (1/255.0f);
	fBlitAntiH(x,y,run);
	}
	x += run;
	runs += run;
	aa += run;
	}
	}

	void SkRasterPipelineBlitter::blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) {
	SkIRect clip = {x,y, x+2,y+1};
	uint8_t coverage[] = { (uint8_t)a0, (uint8_t)a1 };

	SkMask mask;
	mask.fImage = coverage;
	mask.fBounds = clip;
	mask.fRowBytes = 2;
	mask.fFormat = SkMask::kA8_Format;

	this->blitMask(mask, clip);
	}

	void SkRasterPipelineBlitter::blitMask(const SkMask& mask, const SkIRect& clip) {
	if (mask.fFormat == SkMask::kBW_Format) {
	// TODO: native BW masks?
	return INHERITED::blitMask(mask, clip);
	}

	if (mask.fFormat == SkMask::kA8_Format && !fBlitMaskA8) {
	SkRasterPipeline p(fAlloc);
	p.extend(fColorPipeline);
	if (fBlend == SkBlendMode::kSrcOver) {
	p.append(SkRasterPipeline::scale_u8, &fMaskPtr);
	this->append_load_d(&p);
	this->append_blend(&p);
	} else {
	this->append_load_d(&p);
	this->append_blend(&p);
	p.append(SkRasterPipeline::lerp_u8, &fMaskPtr);
	}
	this->maybe_clamp(&p);
	this->append_store(&p);
	fBlitMaskA8 = p.compile();
	}

	if (mask.fFormat == SkMask::kLCD16_Format && !fBlitMaskLCD16) {
	SkRasterPipeline p(fAlloc);
	p.extend(fColorPipeline);
	this->append_load_d(&p);
	this->append_blend(&p);
	p.append(SkRasterPipeline::lerp_565, &fMaskPtr);
	this->maybe_clamp(&p);
	this->append_store(&p);
	fBlitMaskLCD16 = p.compile();
	}

	int x = clip.left();
	for (int y = clip.top(); y < clip.bottom(); y++) {
	fDstPtr = fDst.writable_addr(0,y);

	this->maybe_shade(x,y,clip.width());
	switch (mask.fFormat) {
	case SkMask::kA8_Format:
	fMaskPtr = mask.getAddr8(x,y)-x;
	fBlitMaskA8(x,y,clip.width());
	break;
	case SkMask::kLCD16_Format:
	fMaskPtr = mask.getAddrLCD16(x,y)-x;
	fBlitMaskLCD16(x,y,clip.width());
	break;
	default:
	// TODO
	break;
	}
	}
	}