src/shaders/SkImageShader.cpp

/*
 * 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 "src/shaders/SkImageShader.h"

#include "include/core/SkAlphaType.h"
#include "include/core/SkBitmap.h"
#include "include/core/SkBlendMode.h"
#include "include/core/SkColorType.h"
#include "include/core/SkMatrix.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPixmap.h"
#include "include/core/SkScalar.h"
#include "include/core/SkShader.h"
#include "include/core/SkTileMode.h"
#include "include/private/SkMath.h"
#include "modules/skcms/skcms.h"
#include "src/core/SkArenaAlloc.h"
#include "src/core/SkBitmapProcState.h"
#include "src/core/SkColorSpaceXformSteps.h"
#include "src/core/SkEffectPriv.h"
#include "src/core/SkImageInfoPriv.h"
#include "src/core/SkMipmapAccessor.h"
#include "src/core/SkPicturePriv.h"
#include "src/core/SkRasterPipeline.h"
#include "src/core/SkRasterPipelineOpContexts.h"
#include "src/core/SkRasterPipelineOpList.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSamplingPriv.h"
#include "src/core/SkWriteBuffer.h"
#include "src/image/SkImage_Base.h"

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT
#include "src/shaders/SkBitmapProcShader.h"
#endif

#include <optional>
#include <tuple>
#include <utility>

class SkColorSpace;

SkM44 SkImageShader::CubicResamplerMatrix(float B, float C) {
#if 0
    constexpr SkM44 kMitchell = SkM44( 1.f/18.f, -9.f/18.f,  15.f/18.f,  -7.f/18.f,
                                      16.f/18.f,  0.f/18.f, -36.f/18.f,  21.f/18.f,
                                       1.f/18.f,  9.f/18.f,  27.f/18.f, -21.f/18.f,
                                       0.f/18.f,  0.f/18.f,  -6.f/18.f,   7.f/18.f);

    constexpr SkM44 kCatmull = SkM44(0.0f, -0.5f,  1.0f, -0.5f,
                                     1.0f,  0.0f, -2.5f,  1.5f,
                                     0.0f,  0.5f,  2.0f, -1.5f,
                                     0.0f,  0.0f, -0.5f,  0.5f);

    if (B == 1.0f/3 && C == 1.0f/3) {
        return kMitchell;
    }
    if (B == 0 && C == 0.5f) {
        return kCatmull;
    }
#endif
    return SkM44(    (1.f/6)*B, -(3.f/6)*B - C,       (3.f/6)*B + 2*C,    - (1.f/6)*B - C,
                 1 - (2.f/6)*B,              0, -3 + (12.f/6)*B +   C,  2 - (9.f/6)*B - C,
                     (1.f/6)*B,  (3.f/6)*B + C,  3 - (15.f/6)*B - 2*C, -2 + (9.f/6)*B + C,
                             0,              0,                    -C,      (1.f/6)*B + C);
}

/**
 *  We are faster in clamp, so always use that tiling when we can.
 */
static SkTileMode optimize(SkTileMode tm, int dimension) {
    SkASSERT(dimension > 0);
#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
    // need to update frameworks/base/libs/hwui/tests/unit/SkiaBehaviorTests.cpp:55 to allow
    // for transforming to clamp.
    return tm;
#else
    // mirror and repeat on a 1px axis are the same as clamping, but decal will still transition to
    // transparent black.
    return (tm != SkTileMode::kDecal && dimension == 1) ? SkTileMode::kClamp : tm;
#endif
}

#if defined(SK_DEBUG)
static bool needs_subset(SkImage* img, const SkRect& subset) {
    return subset != SkRect::Make(img->dimensions());
}
#endif

SkImageShader::SkImageShader(sk_sp<SkImage> img,
                             const SkRect& subset,
                             SkTileMode tmx, SkTileMode tmy,
                             const SkSamplingOptions& sampling,
                             bool raw,
                             bool clampAsIfUnpremul)
        : fImage(std::move(img))
        , fSampling(sampling)
        , fTileModeX(optimize(tmx, fImage->width()))
        , fTileModeY(optimize(tmy, fImage->height()))
        , fSubset(subset)
        , fRaw(raw)
        , fClampAsIfUnpremul(clampAsIfUnpremul) {
    // These options should never appear together:
    SkASSERT(!fRaw || !fClampAsIfUnpremul);

    // Bicubic filtering of raw image shaders would add a surprising clamp - so we don't support it
    SkASSERT(!fRaw || !fSampling.useCubic);
}

// just used for legacy-unflattening
enum class LegacyFilterEnum {
    kNone,
    kLow,
    kMedium,
    kHigh,
    // this is the special value for backward compatibility
    kInheritFromPaint,
    // this signals we should use the new SkFilterOptions
    kUseFilterOptions,
    // use cubic and ignore FilterOptions
    kUseCubicResampler,

    kLast = kUseCubicResampler,
};

// fClampAsIfUnpremul is always false when constructed through public APIs,
// so there's no need to read or write it here.

sk_sp<SkFlattenable> SkImageShader::CreateProc(SkReadBuffer& buffer) {
    auto tmx = buffer.read32LE<SkTileMode>(SkTileMode::kLastTileMode);
    auto tmy = buffer.read32LE<SkTileMode>(SkTileMode::kLastTileMode);

    SkSamplingOptions sampling;
    bool readSampling = true;
    if (buffer.isVersionLT(SkPicturePriv::kNoFilterQualityShaders_Version) &&
        !buffer.readBool() /* legacy has_sampling */)
    {
        readSampling = false;
        // we just default to Nearest in sampling
    }
    if (readSampling) {
        sampling = buffer.readSampling();
    }

    SkMatrix localMatrix;
    if (buffer.isVersionLT(SkPicturePriv::Version::kNoShaderLocalMatrix)) {
        buffer.readMatrix(&localMatrix);
    }
    sk_sp<SkImage> img = buffer.readImage();
    if (!img) {
        return nullptr;
    }

    bool raw = buffer.isVersionLT(SkPicturePriv::Version::kRawImageShaders) ? false
                                                                            : buffer.readBool();

    // TODO(skbug.com/40043877): Subset is not serialized yet; it's only used by special images so it
    // will never be written to an SKP.

    return raw ? SkImageShader::MakeRaw(std::move(img), tmx, tmy, sampling, &localMatrix)
               : SkImageShader::Make(std::move(img), tmx, tmy, sampling, &localMatrix);
}

void SkImageShader::flatten(SkWriteBuffer& buffer) const {
    buffer.writeUInt((unsigned)fTileModeX);
    buffer.writeUInt((unsigned)fTileModeY);

    buffer.writeSampling(fSampling);

    buffer.writeImage(fImage.get());
    SkASSERT(fClampAsIfUnpremul == false);

    // TODO(skbug.com/40043877): Subset is not serialized yet; it's only used by special images so it
    // will never be written to an SKP.
    SkASSERT(!needs_subset(fImage.get(), fSubset));

    buffer.writeBool(fRaw);
}

bool SkImageShader::isOpaque() const {
    return fImage->isOpaque() &&
           fTileModeX != SkTileMode::kDecal && fTileModeY != SkTileMode::kDecal;
}

#ifdef SK_ENABLE_LEGACY_SHADERCONTEXT

static bool legacy_shader_can_handle(const SkMatrix& inv) {
    SkASSERT(!inv.hasPerspective());

    // Scale+translate methods are always present, but affine might not be.
    if (!SkOpts::S32_alpha_D32_filter_DXDY && !inv.isScaleTranslate()) {
        return false;
    }

    // legacy code uses SkFixed 32.32, so ensure the inverse doesn't map device coordinates
    // out of range.
    const SkScalar max_dev_coord = 32767.0f;
    const SkRect src = inv.mapRect(SkRect::MakeWH(max_dev_coord, max_dev_coord));

    // take 1/4 of max signed 32bits so we have room to subtract local values
    const SkScalar max_fixed32dot32 = float(SK_MaxS32) * 0.25f;
    if (!SkRect::MakeLTRB(-max_fixed32dot32, -max_fixed32dot32,
                          +max_fixed32dot32, +max_fixed32dot32).contains(src)) {
        return false;
    }

    // legacy shader impl should be able to handle these matrices
    return true;
}

SkShaderBase::Context* SkImageShader::onMakeContext(const ContextRec& rec,
                                                    SkArenaAlloc* alloc) const {
    SkASSERT(!needs_subset(fImage.get(), fSubset)); // TODO(skbug.com/40043877)
    if (fImage->alphaType() == kUnpremul_SkAlphaType) {
        return nullptr;
    }
    if (fImage->colorType() != kN32_SkColorType) {
        return nullptr;
    }
    if (fTileModeX != fTileModeY) {
        return nullptr;
    }
    if (fTileModeX == SkTileMode::kDecal || fTileModeY == SkTileMode::kDecal) {
        return nullptr;
    }

    SkSamplingOptions sampling = fSampling;
    if (sampling.isAniso()) {
        sampling = SkSamplingPriv::AnisoFallback(fImage->hasMipmaps());
    }

    auto supported = [](const SkSamplingOptions& sampling) {
        const std::tuple<SkFilterMode,SkMipmapMode> supported[] = {
            {SkFilterMode::kNearest, SkMipmapMode::kNone},    // legacy None
            {SkFilterMode::kLinear,  SkMipmapMode::kNone},    // legacy Low
            {SkFilterMode::kLinear,  SkMipmapMode::kNearest}, // legacy Medium
        };
        for (auto [f, m] : supported) {
            if (sampling.filter == f && sampling.mipmap == m) {
                return true;
            }
        }
        return false;
    };
    if (sampling.useCubic || !supported(sampling)) {
        return nullptr;
    }

    // SkBitmapProcShader stores bitmap coordinates in a 16bit buffer,
    // so it can't handle bitmaps larger than 65535.
    //
    // We back off another bit to 32767 to make small amounts of
    // intermediate math safe, e.g. in
    //
    //     SkFixed fx = ...;
    //     fx = tile(fx + SK_Fixed1);
    //
    // we want to make sure (fx + SK_Fixed1) never overflows.
    if (fImage-> width() > 32767 ||
        fImage->height() > 32767) {
        return nullptr;
    }

    auto inv = rec.fMatrixRec.totalInverse();
    if (!inv || !legacy_shader_can_handle(*inv)) {
        return nullptr;
    }

    if (!rec.isLegacyCompatible(fImage->colorSpace())) {
        return nullptr;
    }

    return SkBitmapProcLegacyShader::MakeContext(*this, fTileModeX, fTileModeY, sampling,
                                                 as_IB(fImage.get()), rec, alloc);
}
#endif

SkImage* SkImageShader::onIsAImage(SkMatrix* texM, SkTileMode xy[]) const {
    if (texM) {
        *texM = SkMatrix::I();
    }
    if (xy) {
        xy[0] = fTileModeX;
        xy[1] = fTileModeY;
    }
    return const_cast<SkImage*>(fImage.get());
}

sk_sp<SkShader> SkImageShader::Make(sk_sp<SkImage> image,
                                    SkTileMode tmx, SkTileMode tmy,
                                    const SkSamplingOptions& options,
                                    const SkMatrix* localMatrix,
                                    bool clampAsIfUnpremul) {
    SkRect subset = image ? SkRect::Make(image->dimensions()) : SkRect::MakeEmpty();
    return MakeSubset(std::move(image), subset, tmx, tmy, options, localMatrix, clampAsIfUnpremul);
}

sk_sp<SkShader> SkImageShader::MakeRaw(sk_sp<SkImage> image,
                                       SkTileMode tmx, SkTileMode tmy,
                                       const SkSamplingOptions& options,
                                       const SkMatrix* localMatrix) {
    if (options.useCubic) {
        return nullptr;
    }
    if (!image) {
        return SkShaders::Empty();
    }
    auto subset = SkRect::Make(image->dimensions());

    sk_sp<SkShader> s = sk_make_sp<SkImageShader>(image,
                                                  subset,
                                                  tmx, tmy,
                                                  options,
                                                  /*raw=*/true,
                                                  /*clampAsIfUnpremul=*/false);
    return s->makeWithLocalMatrix(localMatrix ? *localMatrix : SkMatrix::I());
}

sk_sp<SkShader> SkImageShader::MakeSubset(sk_sp<SkImage> image,
                                          const SkRect& subset,
                                          SkTileMode tmx, SkTileMode tmy,
                                          const SkSamplingOptions& options,
                                          const SkMatrix* localMatrix,
                                          bool clampAsIfUnpremul) {
    auto is_unit = [](float x) {
        return x >= 0 && x <= 1;
    };
    if (options.useCubic) {
        if (!is_unit(options.cubic.B) || !is_unit(options.cubic.C)) {
            return nullptr;
        }
    }
    if (!image || subset.isEmpty()) {
        return SkShaders::Empty();
    }

    // Validate subset and check if we can drop it
    if (!SkRect::Make(image->bounds()).contains(subset)) {
        return nullptr;
    }

    sk_sp<SkShader> s = sk_make_sp<SkImageShader>(std::move(image),
                                                  subset,
                                                  tmx, tmy,
                                                  options,
                                                  /*raw=*/false,
                                                  clampAsIfUnpremul);
    return s->makeWithLocalMatrix(localMatrix ? *localMatrix : SkMatrix::I());
}

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

std::pair<SkRect, sk_sp<SkShader>> SkImageShader::MakeForDrawRect(const SkImage* image,
                                                                  const SkPaint& paint,
                                                                  const SkSamplingOptions& sampling,
                                                                  SkRect src,
                                                                  SkRect dst,
                                                                  bool strictSrcSubset) {
    SkASSERT(image);
    // The paint should have already been cleaned for a regular drawImageRect, e.g. no path
    // effect and is a fill.
    SkASSERT(paint.getStyle() == SkPaint::kFill_Style && !paint.getPathEffect());

    SkRect imgBounds = SkRect::Make(image->bounds());

    SkASSERT(src.isFinite() && dst.isFinite() && dst.isSorted());
    SkMatrix localMatrix = SkMatrix::RectToRectOrIdentity(src, dst);
    if (!imgBounds.contains(src)) {
        if (!src.intersect(imgBounds)) {
            return {SkRect::MakeEmpty(), nullptr};  // Nothing to draw for this entry
        }
        // Update dst to match smaller src
        dst = localMatrix.mapRect(src);
    }

    bool imageIsAlphaOnly = SkColorTypeIsAlphaOnly(image->colorType());

    sk_sp<SkShader> imgShader;
    if (strictSrcSubset) {
        imgShader = SkImageShader::MakeSubset(sk_ref_sp(image), src,
                                              SkTileMode::kClamp, SkTileMode::kClamp,
                                              sampling, &localMatrix);
    } else {
        imgShader = image->makeShader(SkTileMode::kClamp, SkTileMode::kClamp,
                                      sampling, &localMatrix);
    }
    if (!imgShader) {
        return {SkRect::MakeEmpty(), nullptr};
    }
    if (imageIsAlphaOnly && paint.getShader()) {
        // Compose the image shader with the paint's shader. Alpha images+shaders should output the
        // texture's alpha multiplied by the shader's color. DstIn (d*sa) will achieve this with
        // the source image and dst shader (MakeBlend takes dst first, src second).
        imgShader = SkShaders::Blend(SkBlendMode::kDstIn, paint.refShader(), std::move(imgShader));
    }
    return {dst, std::move(imgShader)};
}

void SkShaderBase::RegisterFlattenables() { SK_REGISTER_FLATTENABLE(SkImageShader); }

namespace {

struct MipLevelHelper {
    SkPixmap pm;
    SkMatrix inv;
    SkRasterPipelineContexts::GatherCtx* gather;
    SkRasterPipelineContexts::TileCtx* limitX;
    SkRasterPipelineContexts::TileCtx* limitY;
    SkRasterPipelineContexts::DecalTileCtx* decalCtx = nullptr;

    void allocAndInit(SkArenaAlloc* alloc,
                      const SkSamplingOptions& sampling,
                      SkTileMode tileModeX,
                      SkTileMode tileModeY) {
        gather = alloc->make<SkRasterPipelineContexts::GatherCtx>();
        gather->pixels = pm.addr();
        gather->stride = pm.rowBytesAsPixels();
        gather->width = pm.width();
        gather->height = pm.height();

        if (sampling.useCubic) {
            SkImageShader::CubicResamplerMatrix(sampling.cubic.B, sampling.cubic.C)
                    .getColMajor(gather->weights);
        }

        limitX = alloc->make<SkRasterPipelineContexts::TileCtx>();
        limitY = alloc->make<SkRasterPipelineContexts::TileCtx>();
        limitX->scale = pm.width();
        limitX->invScale = 1.0f / pm.width();
        limitY->scale = pm.height();
        limitY->invScale = 1.0f / pm.height();

        // We would like an image that is mapped 1:1 with device pixels but at a half pixel offset
        // to select every pixel from the src image once. Our rasterizer biases upward. That is a
        // rect from 0.5...1.5 fills pixel 1 and not pixel 0. So we make exact integer pixel sample
        // values select the pixel to the left/above the integer value.
        //
        // Note that a mirror mapping between canvas and image space will not have this property -
        // on one side of the image a row/column will be skipped and one repeated on the other side.
        //
        // The GM nearest_half_pixel_image tests both of the above scenarios.
        //
        // The implementation of SkTileMode::kMirror also modifies integer pixel snapping to create
        // consistency when the sample coords are running backwards and must account for gather
        // modification we perform here. The GM mirror_tile tests this.
        if (!sampling.useCubic && sampling.filter == SkFilterMode::kNearest) {
            gather->roundDownAtInteger = true;
            limitX->mirrorBiasDir = limitY->mirrorBiasDir = 1;
        }

        if (tileModeX == SkTileMode::kDecal || tileModeY == SkTileMode::kDecal) {
            decalCtx = alloc->make<SkRasterPipelineContexts::DecalTileCtx>();
            decalCtx->limit_x = limitX->scale;
            decalCtx->limit_y = limitY->scale;

            // When integer sample coords snap left/up then we want the right/bottom edge of the
            // image bounds to be inside the image rather than the left/top edge, that is (0, w]
            // rather than [0, w).
            if (gather->roundDownAtInteger) {
                decalCtx->inclusiveEdge_x = decalCtx->limit_x;
                decalCtx->inclusiveEdge_y = decalCtx->limit_y;
            }
        }
    }
};

}  // namespace

static SkSamplingOptions tweak_sampling(SkSamplingOptions sampling, const SkMatrix& matrix) {
    SkFilterMode filter = sampling.filter;

    // When the matrix is just an integer translate, bilerp == nearest neighbor.
    if (filter == SkFilterMode::kLinear &&
            matrix.getType() <= SkMatrix::kTranslate_Mask &&
            matrix.getTranslateX() == (int)matrix.getTranslateX() &&
            matrix.getTranslateY() == (int)matrix.getTranslateY()) {
        filter = SkFilterMode::kNearest;
    }

    return SkSamplingOptions(filter, sampling.mipmap);
}

bool SkImageShader::appendStages(const SkStageRec& rec, const SkShaders::MatrixRec& mRec) const {
    SkASSERT(!needs_subset(fImage.get(), fSubset));  // TODO(skbug.com/40043877)

    // We only support certain sampling options in stages so far
    auto sampling = fSampling;
    if (sampling.isAniso()) {
        sampling = SkSamplingPriv::AnisoFallback(fImage->hasMipmaps());
    }

    SkRasterPipeline* p = rec.fPipeline;
    SkArenaAlloc* alloc = rec.fAlloc;

    SkMatrix baseInv;
    // If the total matrix isn't valid then we will always access the base MIP level.
    if (mRec.totalMatrixIsValid()) {
        auto inv = mRec.totalInverse();
        if (!inv) {
            return false;
        }
        baseInv = *inv;
        baseInv.normalizePerspective();
    }

    SkASSERT(!sampling.useCubic || sampling.mipmap == SkMipmapMode::kNone);
    auto* access = SkMipmapAccessor::Make(alloc, fImage.get(), baseInv, sampling.mipmap);
    if (!access) {
        return false;
    }

    MipLevelHelper upper;
    std::tie(upper.pm, upper.inv) = access->level();

    const bool coordsAlreadySeeded = mRec.rasterPipelineCoordsAreSeeded();
    const SkMatrix totalInv = SkMatrix::Concat(upper.inv, baseInv);
    if (!sampling.useCubic) {
        // TODO: can tweak_sampling sometimes for cubic too when B=0
        if (mRec.totalMatrixIsValid()) {
            sampling = tweak_sampling(sampling, totalInv);
        }
    }

    if (!mRec.apply(rec, upper.inv)) {
        return false;
    }

    upper.allocAndInit(alloc, sampling, fTileModeX, fTileModeY);

    MipLevelHelper lower;
    SkRasterPipelineContexts::MipmapCtx* mipmapCtx = nullptr;
    float lowerWeight = access->lowerWeight();
    if (lowerWeight > 0) {
        std::tie(lower.pm, lower.inv) = access->lowerLevel();
        mipmapCtx = alloc->make<SkRasterPipelineContexts::MipmapCtx>();
        mipmapCtx->lowerWeight = lowerWeight;
        mipmapCtx->scaleX = static_cast<float>(lower.pm.width()) / upper.pm.width();
        mipmapCtx->scaleY = static_cast<float>(lower.pm.height()) / upper.pm.height();

        lower.allocAndInit(alloc, sampling, fTileModeX, fTileModeY);

        p->append(SkRasterPipelineOp::mipmap_linear_init, mipmapCtx);
    }

    const bool decalBothAxes = fTileModeX == SkTileMode::kDecal && fTileModeY == SkTileMode::kDecal;

    auto append_tiling_and_gather = [&](const MipLevelHelper* level) {
        if (decalBothAxes) {
            p->append(SkRasterPipelineOp::decal_x_and_y,  level->decalCtx);
        } else {
            switch (fTileModeX) {
                case SkTileMode::kClamp: /* The gather_xxx stage will clamp for us. */
                    break;
                case SkTileMode::kMirror:
                    p->append(SkRasterPipelineOp::mirror_x, level->limitX);
                    break;
                case SkTileMode::kRepeat:
                    p->append(SkRasterPipelineOp::repeat_x, level->limitX);
                    break;
                case SkTileMode::kDecal:
                    p->append(SkRasterPipelineOp::decal_x, level->decalCtx);
                    break;
            }
            switch (fTileModeY) {
                case SkTileMode::kClamp: /* The gather_xxx stage will clamp for us. */
                    break;
                case SkTileMode::kMirror:
                    p->append(SkRasterPipelineOp::mirror_y, level->limitY);
                    break;
                case SkTileMode::kRepeat:
                    p->append(SkRasterPipelineOp::repeat_y, level->limitY);
                    break;
                case SkTileMode::kDecal:
                    p->append(SkRasterPipelineOp::decal_y, level->decalCtx);
                    break;
            }
        }

        void* ctx = level->gather;
        switch (level->pm.colorType()) {
            case kAlpha_8_SkColorType:      p->append(SkRasterPipelineOp::gather_a8,    ctx); break;
            case kA16_unorm_SkColorType:    p->append(SkRasterPipelineOp::gather_a16,   ctx); break;
            case kA16_float_SkColorType:    p->append(SkRasterPipelineOp::gather_af16,  ctx); break;
            case kR16_float_SkColorType:    p->append(SkRasterPipelineOp::gather_rf16,  ctx); break;
            case kRGB_565_SkColorType:      p->append(SkRasterPipelineOp::gather_565,   ctx); break;
            case kARGB_4444_SkColorType:    p->append(SkRasterPipelineOp::gather_4444,  ctx); break;
            case kR8G8_unorm_SkColorType:   p->append(SkRasterPipelineOp::gather_rg88,  ctx); break;
            case kR16_unorm_SkColorType:    p->append(SkRasterPipelineOp::gather_r16,   ctx); break;
            case kR16G16_unorm_SkColorType: p->append(SkRasterPipelineOp::gather_rg1616,ctx); break;
            case kR16G16_float_SkColorType: p->append(SkRasterPipelineOp::gather_rgf16, ctx); break;
            case kRGBA_8888_SkColorType:    p->append(SkRasterPipelineOp::gather_8888,  ctx); break;

            case kRGBA_1010102_SkColorType:
                p->append(SkRasterPipelineOp::gather_1010102, ctx);
                break;

            case kR16G16B16A16_unorm_SkColorType:
                p->append(SkRasterPipelineOp::gather_16161616, ctx);
                break;

            case kRGBA_F16Norm_SkColorType:
            case kRGBA_F16_SkColorType:     p->append(SkRasterPipelineOp::gather_f16,   ctx); break;
            case kRGBA_F32_SkColorType:     p->append(SkRasterPipelineOp::gather_f32,   ctx); break;
            case kBGRA_10101010_XR_SkColorType:
                p->append(SkRasterPipelineOp::gather_10101010_xr,  ctx);
                p->append(SkRasterPipelineOp::swap_rb);
                break;
            case kRGBA_10x6_SkColorType:    p->append(SkRasterPipelineOp::gather_10x6,  ctx); break;

            case kGray_8_SkColorType:       p->append(SkRasterPipelineOp::gather_a8,    ctx);
                                            p->append(SkRasterPipelineOp::alpha_to_gray    ); break;

            case kR8_unorm_SkColorType:     p->append(SkRasterPipelineOp::gather_a8,    ctx);
                                            p->append(SkRasterPipelineOp::alpha_to_red     ); break;

            case kRGB_888x_SkColorType:     p->append(SkRasterPipelineOp::gather_8888,  ctx);
                                            p->append(SkRasterPipelineOp::force_opaque     ); break;
            case kRGB_F16F16F16x_SkColorType:
                p->append(SkRasterPipelineOp::gather_f16,  ctx);
                p->append(SkRasterPipelineOp::force_opaque);
                break;
            case kBGRA_1010102_SkColorType:
                p->append(SkRasterPipelineOp::gather_1010102, ctx);
                p->append(SkRasterPipelineOp::swap_rb);
                break;

            case kRGB_101010x_SkColorType:
                p->append(SkRasterPipelineOp::gather_1010102, ctx);
                p->append(SkRasterPipelineOp::force_opaque);
                break;

            case kBGR_101010x_XR_SkColorType:
                p->append(SkRasterPipelineOp::gather_1010102_xr, ctx);
                p->append(SkRasterPipelineOp::force_opaque);
                p->append(SkRasterPipelineOp::swap_rb);
                break;

            case kBGR_101010x_SkColorType:
                p->append(SkRasterPipelineOp::gather_1010102, ctx);
                p->append(SkRasterPipelineOp::force_opaque);
                p->append(SkRasterPipelineOp::swap_rb);
                break;

            case kBGRA_8888_SkColorType:
                p->append(SkRasterPipelineOp::gather_8888, ctx);
                p->append(SkRasterPipelineOp::swap_rb);
                break;

            case kSRGBA_8888_SkColorType:
                p->append(SkRasterPipelineOp::gather_8888, ctx);
                p->appendTransferFunction(*skcms_sRGB_TransferFunction());
                break;

            case kUnknown_SkColorType: SkASSERT(false);
        }
        if (level->decalCtx) {
            p->append(SkRasterPipelineOp::check_decal_mask, level->decalCtx);
        }
    };

    auto append_misc = [&] {
        SkColorSpace* cs = upper.pm.colorSpace();
        SkAlphaType   at = upper.pm.alphaType();

        // Color for alpha-only images comes from the paint (already converted to dst color space).
        // If we were sampled by a runtime effect, the paint color was replaced with transparent
        // black, so this tinting is effectively suppressed. See also: RuntimeEffectRPCallbacks
        if (SkColorTypeIsAlphaOnly(upper.pm.colorType()) && !fRaw) {
            p->appendSetRGB(alloc, rec.fPaintColor);

            cs = rec.fDstCS;
            at = kUnpremul_SkAlphaType;
        }

        // Bicubic filtering naturally produces out of range values on both sides of [0,1].
        if (sampling.useCubic) {
            p->append(at == kUnpremul_SkAlphaType || fClampAsIfUnpremul
                          ? SkRasterPipelineOp::clamp_01
                          : SkRasterPipelineOp::clamp_gamut);
        }

        // Transform color space and alpha type to match shader convention (dst CS, premul alpha).
        if (!fRaw) {
            alloc->make<SkColorSpaceXformSteps>(cs, at, rec.fDstCS, kPremul_SkAlphaType)->apply(p);
        }

        return true;
    };

    // Check for fast-path stages.
    // TODO: Could we use the fast-path stages for each level when doing linear mipmap filtering?
    SkColorType ct = upper.pm.colorType();
    if ((ct == kRGBA_8888_SkColorType || ct == kBGRA_8888_SkColorType) &&
        !sampling.useCubic && sampling.filter == SkFilterMode::kLinear &&
        sampling.mipmap != SkMipmapMode::kLinear &&
        fTileModeX == SkTileMode::kClamp && fTileModeY == SkTileMode::kClamp) {
        // Check bounding box of points we will sample to see if we can use lowp
        // and not over/under flow.
        bool shouldUseHighPBilerp = false;
        if (!rec.fDstBounds.isEmpty()) {
            std::array<SkPoint, 4> quad = rec.fDstBounds.toQuad();
            baseInv.mapPoints(quad);
            SkRect deviceImageSpace;
            deviceImageSpace.setBounds(quad);
            for (float val : SkSpan<const float>(deviceImageSpace.asScalars(), 4)) {
                if (val > INT16_MAX || val < INT16_MIN || !std::isfinite(val)) {
                    shouldUseHighPBilerp = true;
                    break;
                }
            }
        }

        const bool uniformY = !coordsAlreadySeeded && mRec.totalMatrixIsValid() &&
                              !mRec.totalMatrix().hasPerspective() && !totalInv.hasPerspective() &&
                              totalInv.getSkewY() == 0;
        if (shouldUseHighPBilerp) {
            p->append(SkRasterPipelineOp::bilerp_clamp_8888_force_highp, upper.gather);
        } else if (uniformY) {
            p->append(SkRasterPipelineOp::bilerp_clamp_8888_uniform_y, upper.gather);
        } else {
            p->append(SkRasterPipelineOp::bilerp_clamp_8888, upper.gather);
        }

        if (ct == kBGRA_8888_SkColorType) {
            p->append(SkRasterPipelineOp::swap_rb);
        }
        return append_misc();
    }
    if ((ct == kRGBA_8888_SkColorType || ct == kBGRA_8888_SkColorType) &&
        sampling.useCubic &&
        fTileModeX == SkTileMode::kClamp && fTileModeY == SkTileMode::kClamp) {

        p->append(SkRasterPipelineOp::bicubic_clamp_8888, upper.gather);
        if (ct == kBGRA_8888_SkColorType) {
            p->append(SkRasterPipelineOp::swap_rb);
        }
        return append_misc();
    }

    // This context can be shared by both levels when doing linear mipmap filtering
    SkRasterPipelineContexts::SamplerCtx* sampler =
            alloc->make<SkRasterPipelineContexts::SamplerCtx>();

    auto sample = [&](SkRasterPipelineOp setup_x,
                      SkRasterPipelineOp setup_y,
                      const MipLevelHelper* level) {
        p->append(setup_x, sampler);
        p->append(setup_y, sampler);
        append_tiling_and_gather(level);
        p->append(SkRasterPipelineOp::accumulate, sampler);
    };

    auto sample_level = [&](const MipLevelHelper* level) {
        if (sampling.useCubic) {
            CubicResamplerMatrix(sampling.cubic.B, sampling.cubic.C).getColMajor(sampler->weights);

            p->append(SkRasterPipelineOp::bicubic_setup, sampler);

            sample(SkRasterPipelineOp::bicubic_n3x, SkRasterPipelineOp::bicubic_n3y, level);
            sample(SkRasterPipelineOp::bicubic_n1x, SkRasterPipelineOp::bicubic_n3y, level);
            sample(SkRasterPipelineOp::bicubic_p1x, SkRasterPipelineOp::bicubic_n3y, level);
            sample(SkRasterPipelineOp::bicubic_p3x, SkRasterPipelineOp::bicubic_n3y, level);

            sample(SkRasterPipelineOp::bicubic_n3x, SkRasterPipelineOp::bicubic_n1y, level);
            sample(SkRasterPipelineOp::bicubic_n1x, SkRasterPipelineOp::bicubic_n1y, level);
            sample(SkRasterPipelineOp::bicubic_p1x, SkRasterPipelineOp::bicubic_n1y, level);
            sample(SkRasterPipelineOp::bicubic_p3x, SkRasterPipelineOp::bicubic_n1y, level);

            sample(SkRasterPipelineOp::bicubic_n3x, SkRasterPipelineOp::bicubic_p1y, level);
            sample(SkRasterPipelineOp::bicubic_n1x, SkRasterPipelineOp::bicubic_p1y, level);
            sample(SkRasterPipelineOp::bicubic_p1x, SkRasterPipelineOp::bicubic_p1y, level);
            sample(SkRasterPipelineOp::bicubic_p3x, SkRasterPipelineOp::bicubic_p1y, level);

            sample(SkRasterPipelineOp::bicubic_n3x, SkRasterPipelineOp::bicubic_p3y, level);
            sample(SkRasterPipelineOp::bicubic_n1x, SkRasterPipelineOp::bicubic_p3y, level);
            sample(SkRasterPipelineOp::bicubic_p1x, SkRasterPipelineOp::bicubic_p3y, level);
            sample(SkRasterPipelineOp::bicubic_p3x, SkRasterPipelineOp::bicubic_p3y, level);

            p->append(SkRasterPipelineOp::move_dst_src);
        } else if (sampling.filter == SkFilterMode::kLinear) {
            p->append(SkRasterPipelineOp::bilinear_setup, sampler);

            sample(SkRasterPipelineOp::bilinear_nx, SkRasterPipelineOp::bilinear_ny, level);
            sample(SkRasterPipelineOp::bilinear_px, SkRasterPipelineOp::bilinear_ny, level);
            sample(SkRasterPipelineOp::bilinear_nx, SkRasterPipelineOp::bilinear_py, level);
            sample(SkRasterPipelineOp::bilinear_px, SkRasterPipelineOp::bilinear_py, level);

            p->append(SkRasterPipelineOp::move_dst_src);
        } else {
            append_tiling_and_gather(level);
        }
    };

    sample_level(&upper);

    if (mipmapCtx) {
        p->append(SkRasterPipelineOp::mipmap_linear_update, mipmapCtx);
        sample_level(&lower);
        p->append(SkRasterPipelineOp::mipmap_linear_finish, mipmapCtx);
    }

    return append_misc();
}

namespace SkShaders {

sk_sp<SkShader> Image(sk_sp<SkImage> image,
                      SkTileMode tmx, SkTileMode tmy,
                      const SkSamplingOptions& options,
                      const SkMatrix* localMatrix) {
    return SkImageShader::Make(std::move(image), tmx, tmy, options, localMatrix);
}

sk_sp<SkShader> RawImage(sk_sp<SkImage> image,
                         SkTileMode tmx, SkTileMode tmy,
                         const SkSamplingOptions& options,
                         const SkMatrix* localMatrix) {
    return SkImageShader::MakeRaw(std::move(image), tmx, tmy, options, localMatrix);
}

}  // namespace SkShaders