Simplified linear pipeline.

src/core/SkLinearBitmapPipeline.cpp

Index: src/core/SkLinearBitmapPipeline.cpp
diff --git a/src/core/SkLinearBitmapPipeline.cpp b/src/core/SkLinearBitmapPipeline.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..d1000282da334f286e831cc0029a957662087df0
--- /dev/null
+++ b/src/core/SkLinearBitmapPipeline.cpp
@@ -0,0 +1,449 @@
+/*
+ * 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 "SkLinearBitmapPipeline.h"
+
+struct X {
+    explicit X(SkScalar val) : fVal{val} { }
+    explicit X(SkPoint pt) : fVal{pt.fX} { }
+    explicit X(SkSize s) : fVal{s.fWidth} { }
+    explicit X(SkISize s) : fVal(s.fWidth) { }
+    operator float () const {return fVal;}
+private:
+    float fVal;
+};
+
+struct Y {
+    explicit Y(SkScalar val) : fVal{val} { }
+    explicit Y(SkPoint pt) : fVal{pt.fY} { }
+    explicit Y(SkSize s) : fVal{s.fHeight} { }
+    explicit Y(SkISize s) : fVal(s.fHeight) { }
+
+    operator float () const {return fVal;}
+private:
+    float fVal;
+};
+
+template<typename Strategy, typename Next>
+class PointProcessor : public PointProcessorInterface {
+public:
+    template <typename... Args>
+    PointProcessor(Next* next, Args&&... args)
+        : fNext{next}
+        , fStrategy{std::forward<Args>(args)...}{ }
+
+    void pointListFew(int n, Sk4fArg xs, Sk4fArg ys) override {
+        Sk4f newXs = xs;
+        Sk4f newYs = ys;
+        fStrategy.processPoints(&newXs, &newYs);
+        fNext->pointListFew(n, newXs, newYs);
+    }
+
+    void pointList4(Sk4fArg xs, Sk4fArg ys) override {
+        Sk4f newXs = xs;
+        Sk4f newYs = ys;
+        fStrategy.processPoints(&newXs, &newYs);
+        fNext->pointList4(newXs, newYs);
+    }
+
+private:
+    Next* const fNext;
+    Strategy fStrategy;
+};
+
+class SkippedStage final : public PointProcessorInterface {
+    void pointListFew(int n, Sk4fArg xs, Sk4fArg ys) override {
+        SkFAIL("Abort tiler.");
+    }
+    void pointList4(Sk4fArg Xs, Sk4fArg Ys) override {
+        SkFAIL("Abort point processor.");
+    }
+};
+
+class TranslateMatrixStrategy {
+public:
+    TranslateMatrixStrategy(SkVector offset)
+        : fXOffset{X(offset)}
+        , fYOffset{Y(offset)} { }
+    void processPoints(Sk4f* xs, Sk4f* ys) {
+        *xs = *xs + fXOffset;
+        *ys = *ys + fYOffset;
+    }
+
+private:
+    const Sk4f fXOffset, fYOffset;
+};
+template <typename Next = PointProcessorInterface>
+using TranslateMatrix = PointProcessor<TranslateMatrixStrategy, Next>;
+
+class ScaleMatrixStrategy {
+public:
+    ScaleMatrixStrategy(SkVector offset, SkVector scale)
+        : fXOffset{X(offset)}, fYOffset{Y(offset)}
+        ,  fXScale{X(scale)},   fYScale{Y(scale)} { }
+    void processPoints(Sk4f* xs, Sk4f* ys) {
+        *xs = *xs * fXScale + fXOffset;
+        *ys = *ys * fYScale + fYOffset;
+    }
+
+private:
+    const Sk4f fXOffset, fYOffset;
+    const Sk4f fXScale, fYScale;
+};
+template <typename Next = PointProcessorInterface>
+using ScaleMatrix = PointProcessor<ScaleMatrixStrategy, Next>;
+
+class AffineMatrixStrategy {
+public:
+    AffineMatrixStrategy(SkVector offset, SkVector scale, SkVector skew)
+        : fXOffset{X(offset)}, fYOffset{Y(offset)}
+        , fXScale{X(scale)},   fYScale{Y(scale)}
+        , fXSkew{X(skew)},     fYSkew{Y(skew)} { }
+    void processPoints(Sk4f* xs, Sk4f* ys) {
+        Sk4f newXs = fXScale * *xs +  fXSkew * *ys + fXOffset;
+        Sk4f newYs =  fYSkew * *xs + fYScale * *ys + fYOffset;
+
+        *xs = newXs;
+        *ys = newYs;
+    }
+
+private:
+    const Sk4f fXOffset, fYOffset;
+    const Sk4f fXScale,  fYScale;
+    const Sk4f fXSkew,   fYSkew;
+};
+template <typename Next = PointProcessorInterface>
+using AffineMatrix = PointProcessor<AffineMatrixStrategy, Next>;
+
+static PointProcessorInterface* choose_matrix(
+    PointProcessorInterface* next,
+    const SkMatrix& inverse,
+    SkLinearBitmapPipeline::MatrixStage* matrixProc) {
+    if (inverse.hasPerspective()) {
+        SkFAIL("Not implemented.");
+    } else if (inverse.getSkewX() != 0.0f || inverse.getSkewY() != 0.0f) {
+        matrixProc->Initialize<AffineMatrix<>>(
+            next,
+            SkVector{inverse.getTranslateX(), inverse.getTranslateY()},
+            SkVector{inverse.getScaleX(), inverse.getScaleY()},
+            SkVector{inverse.getSkewX(), inverse.getSkewY()});
+    } else if (inverse.getScaleX() != 1.0f || inverse.getScaleY() != 1.0f) {
+        matrixProc->Initialize<ScaleMatrix<>>(
+            next,
+            SkVector{inverse.getTranslateX(), inverse.getTranslateY()},
+            SkVector{inverse.getScaleX(), inverse.getScaleY()});
+    } else if (inverse.getTranslateX() != 0.0f || inverse.getTranslateY() != 0.0f) {
+        matrixProc->Initialize<TranslateMatrix<>>(
+            next,
+            SkVector{inverse.getTranslateX(), inverse.getTranslateY()});
+    } else {
+        matrixProc->Initialize<SkippedStage>();
+        return next;
+    }
+    return matrixProc->get();
+}
+
+class ClampStrategy {
+public:
+    ClampStrategy(X max)
+        : fXMin{0.0f}
+        , fXMax{max - 1.0f} { }
+    ClampStrategy(Y max)
+        : fYMin{0.0f}
+        , fYMax{max - 1.0f} { }
+    ClampStrategy(SkSize max)
+        : fXMin{0.0f}
+        , fYMin{0.0f}
+        , fXMax{X(max) - 1.0f}
+        , fYMax{Y(max) - 1.0f} { }
+
+    void processPoints(Sk4f* xs, Sk4f* ys) {
+        *xs = Sk4f::Min(Sk4f::Max(*xs, fXMin), fXMax);
+        *ys = Sk4f::Min(Sk4f::Max(*ys, fYMin), fYMax);
+    }
+
+private:
+    const Sk4f fXMin{SK_FloatNegativeInfinity};
+    const Sk4f fYMin{SK_FloatNegativeInfinity};
+    const Sk4f fXMax{SK_FloatInfinity};
+    const Sk4f fYMax{SK_FloatInfinity};
+};
+template <typename Next = PointProcessorInterface>
+using Clamp = PointProcessor<ClampStrategy, Next>;
+
+class RepeatStrategy {
+public:
+    RepeatStrategy(X max) : fXMax{max}, fXInvMax{1.0f/max} { }
+    RepeatStrategy(Y max) : fYMax{max}, fYInvMax{1.0f/max} { }
+    RepeatStrategy(SkSize max)
+        : fXMax{X(max)}
+        , fXInvMax{1.0f / X(max)}
+        , fYMax{Y(max)}
+        , fYInvMax{1.0f / Y(max)} { }
+
+    void processPoints(Sk4f* xs, Sk4f* ys) {
+        Sk4f divX = (*xs * fXInvMax).floor();
+        Sk4f divY = (*ys * fYInvMax).floor();
+        Sk4f baseX = (divX * fXMax);
+        Sk4f baseY = (divY * fYMax);
+        *xs = *xs - baseX;
+        *ys = *ys - baseY;
+    }
+
+private:
+    const Sk4f fXMax{0.0f};
+    const Sk4f fXInvMax{0.0f};
+    const Sk4f fYMax{0.0f};
+    const Sk4f fYInvMax{0.0f};
+};
+
+template <typename Next = PointProcessorInterface>
+using Repeat = PointProcessor<RepeatStrategy, Next>;
+
+static PointProcessorInterface* choose_tiler(
+    PointProcessorInterface* next,
+    SkSize dimensions,
+    SkShader::TileMode xMode,
+    SkShader::TileMode yMode,
+    SkLinearBitmapPipeline::TileStage* tileProcXOrBoth,
+    SkLinearBitmapPipeline::TileStage* tileProcY) {
+    if (xMode == yMode) {
+        switch (xMode) {
+            case SkShader::kClamp_TileMode:
+                tileProcXOrBoth->Initialize<Clamp<>>(next, dimensions);
+                break;
+            case SkShader::kRepeat_TileMode:
+                tileProcXOrBoth->Initialize<Repeat<>>(next, dimensions);
+                break;
+            case SkShader::kMirror_TileMode:
+                SkFAIL("Not implemented.");
+                break;
+        }
+        tileProcY->Initialize<SkippedStage>();
+    } else {
+        switch (yMode) {
+            case SkShader::kClamp_TileMode:
+                tileProcY->Initialize<Clamp<>>(next, Y(dimensions));
+                break;
+            case SkShader::kRepeat_TileMode:
+                tileProcY->Initialize<Repeat<>>(next, Y(dimensions));
+                break;
+            case SkShader::kMirror_TileMode:
+                SkFAIL("Not implemented.");
+                break;
+        }
+        switch (xMode) {
+            case SkShader::kClamp_TileMode:
+                tileProcXOrBoth->Initialize<Clamp<>>(tileProcY->get(), X(dimensions));
+                break;
+            case SkShader::kRepeat_TileMode:
+                tileProcXOrBoth->Initialize<Repeat<>>(tileProcY->get(), X(dimensions));
+                break;
+            case SkShader::kMirror_TileMode:
+                SkFAIL("Not implemented.");
+                break;
+        }
+    }
+    return tileProcXOrBoth->get();
+}
+
+class sRGBFast {
+public:
+    static Sk4f sRGBToLinear(Sk4fArg pixel) {
+        Sk4f l = pixel * pixel;
+        return Sk4f{l[0], l[1], l[2], pixel[3]};
+    }
+};
+
+template <SkColorProfileType colorProfile>
+class Passthrough8888 {
+public:
+    Passthrough8888(int width, const uint32_t* src)
+        : fSrc{src}, fWidth{width}{ }
+
+    void getFewPixels(int n, Sk4fArg xs, Sk4fArg ys, Sk4f* px0, Sk4f* px1, Sk4f* px2) {
+        Sk4i XIs = SkNx_cast<int, float>(xs);
+        Sk4i YIs = SkNx_cast<int, float>(ys);
+        Sk4i bufferLoc = YIs * fWidth + XIs;
+        switch (n) {
+            case 3:
+                *px2 = getPixel(fSrc, bufferLoc[2]);
+            case 2:
+                *px1 = getPixel(fSrc, bufferLoc[1]);
+            case 1:
+                *px0 = getPixel(fSrc, bufferLoc[0]);
+            default:
+                break;
+        }
+    }
+
+    void get4Pixels(Sk4fArg xs, Sk4fArg ys, Sk4f* px0, Sk4f* px1, Sk4f* px2, Sk4f* px3) {
+        Sk4i XIs = SkNx_cast<int, float>(xs);
+        Sk4i YIs = SkNx_cast<int, float>(ys);
+        Sk4i bufferLoc = YIs * fWidth + XIs;
+        *px0 = getPixel(fSrc, bufferLoc[0]);
+        *px1 = getPixel(fSrc, bufferLoc[1]);
+        *px2 = getPixel(fSrc, bufferLoc[2]);
+        *px3 = getPixel(fSrc, bufferLoc[3]);
+    }
+
+    const uint32_t* row(int y) { return fSrc + y * fWidth[0]; }
+
+private:
+    Sk4f getPixel(const uint32_t* src, int index) {
+        Sk4b bytePixel = Sk4b::Load((uint8_t *)(&src[index]));
+        Sk4f pixel = SkNx_cast<float, uint8_t>(bytePixel);
+        pixel = pixel * Sk4f{1.0f/255.0f};
+        if (colorProfile == kSRGB_SkColorProfileType) {
+            pixel = sRGBFast::sRGBToLinear(pixel);
+        }
+        return pixel;
+    }
+    const uint32_t* const fSrc;
+    const Sk4i fWidth;
+};
+
+template <typename SourceStrategy>
+class Sampler final : public PointProcessorInterface {
+public:
+    template <typename... Args>
+    Sampler(PixelPlacerInterface* next, Args&&... args)
+        : fNext{next}
+        , fStrategy{std::forward<Args>(args)...} { }
+
+    void pointListFew(int n, Sk4fArg xs, Sk4fArg ys) override {
+        SkASSERT(0 < n && n < 4);
+        Sk4f px0, px1, px2;
+        fStrategy.getFewPixels(n, xs, ys, &px0, &px1, &px2);
+        if (n >= 1) fNext->placePixel(px0);
+        if (n >= 2) fNext->placePixel(px1);
+        if (n >= 3) fNext->placePixel(px2);
+    }
+
+    void pointList4(Sk4fArg xs, Sk4fArg ys) override {
+        Sk4f px0, px1, px2, px3;
+        fStrategy.get4Pixels(xs, ys, &px0, &px1, &px2, &px3);
+        fNext->place4Pixels(px0, px1, px2, px3);
+    }
+
+private:
+    PixelPlacerInterface* const fNext;
+    SourceStrategy fStrategy;
+};
+
+static PointProcessorInterface* choose_pixel_sampler(
+    PixelPlacerInterface* next,
+    const SkImageInfo& imageInfo,
+    const void* imageData,
+    SkLinearBitmapPipeline::SampleStage* sampleStage) {
+    switch (imageInfo.colorType()) {
+        case kRGBA_8888_SkColorType:
+        case kBGRA_8888_SkColorType:
+            if (kN32_SkColorType == imageInfo.colorType()) {
+                if (imageInfo.profileType() == kSRGB_SkColorProfileType) {
+                    sampleStage->Initialize<Sampler<Passthrough8888<kSRGB_SkColorProfileType>>>(
+                        next, imageInfo.width(),
+                        (uint32_t*)imageData);
+                } else {
+                    sampleStage->Initialize<Sampler<Passthrough8888<kLinear_SkColorProfileType>>>(
+                        next, imageInfo.width(),
+                        (uint32_t*)imageData);
+                }
+            } else {
+                SkFAIL("Not implemented. No 8888 Swizzle");
+            }
+            break;
+        default:
+            SkFAIL("Not implemented. Unsupported src");
+            break;
+    }
+    return sampleStage->get();
+}
+
+template <SkAlphaType alphaType>
+class PlaceFPPixel final : public PixelPlacerInterface {
+public:
+    void placePixel(Sk4fArg pixel) override {
+        PlacePixel(fDst, pixel, 0);
+        fDst += 1;
+    }
+
+    void place4Pixels(Sk4fArg p0, Sk4fArg p1, Sk4fArg p2, Sk4fArg p3) override {
+        SkPM4f* dst = fDst;
+        PlacePixel(dst, p0, 0);
+        PlacePixel(dst, p1, 1);
+        PlacePixel(dst, p2, 2);
+        PlacePixel(dst, p3, 3);
+        fDst += 4;
+    }
+
+    void setDestination(SkPM4f* dst) override {
+        fDst = dst;
+    }
+
+private:
+    static void PlacePixel(SkPM4f* dst, Sk4fArg pixel, int index) {
+        Sk4f newPixel = pixel;
+        if (alphaType == kUnpremul_SkAlphaType) {
+            newPixel = Premultiply(pixel);
+        }
+        newPixel.store(dst + index);
+    }
+    static Sk4f Premultiply(Sk4fArg pixel) {
+        float alpha = pixel[3];
+        return pixel * Sk4f{alpha, alpha, alpha, 1.0f};
+    }
+
+    SkPM4f* fDst;
+};
+
+static PixelPlacerInterface* choose_pixel_placer(
+    SkAlphaType alphaType,
+    SkLinearBitmapPipeline::PixelStage* placerStage) {
+    if (alphaType == kUnpremul_SkAlphaType) {
+        placerStage->Initialize<PlaceFPPixel<kUnpremul_SkAlphaType>>();
+    } else {
+        // kOpaque_SkAlphaType is treated the same as kPremul_SkAlphaType
+        placerStage->Initialize<PlaceFPPixel<kPremul_SkAlphaType>>();
+    }
+    return placerStage->get();
+}
+
+SkLinearBitmapPipeline::SkLinearBitmapPipeline(
+    const SkMatrix& inverse,
+    SkShader::TileMode xTile, SkShader::TileMode yTile,
+    const SkImageInfo& srcImageInfo,
+    const void* srcImageData) {
+    SkSize size;
+    size = srcImageInfo.dimensions();
+
+    // As the stages are built, the chooser function may skip a stage. For example, with the
+    // identity matrix, the matrix stage is skipped, and the tilerStage is the first stage.
+    auto placementStage = choose_pixel_placer(srcImageInfo.alphaType(), &fPixelStage);
+    auto samplerStage   = choose_pixel_sampler(placementStage, srcImageInfo,
+                                               srcImageData, &fSampleStage);
+    auto tilerStage     = choose_tiler(samplerStage, size, xTile, yTile, &fTileXOrBothStage,
+                                       &fTileYStage);
+    fFirstStage         = choose_matrix(tilerStage, inverse, &fMatrixStage);
+}
+
+void SkLinearBitmapPipeline::shadeSpan4f(int x, int y, SkPM4f* dst, int count) {
+    fPixelStage->setDestination(dst);
+
+    Sk4f Xs = Sk4f(x) + Sk4f{0.5f, 1.5f, 2.5f, 3.5f};
+    Sk4f Ys(y);
+    Sk4f fours{4.0f};
+
+    while (count >= 4) {
+        fFirstStage->pointList4(Xs, Ys);
+        Xs = Xs + fours;
+        count -= 4;
+    }
+    if (count > 0) {
+        fFirstStage->pointListFew(count, Xs, Ys);
+    }
+}