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* Copyright 2019 Google LLC
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "src/core/SkImageFilterTypes.h"
#include "include/core/SkImage.h"
#include "include/core/SkPicture.h"
#include "include/core/SkShader.h"
#include "include/core/SkTileMode.h"
#include "src/core/SkColorFilterBase.h"
#include "src/core/SkImageFilter_Base.h"
#include "src/core/SkMatrixPriv.h"
#include "src/core/SkRectPriv.h"
#include "src/core/SkSpecialSurface.h"
namespace skif {
namespace {
// This exists to cover up issues where infinite precision would produce integers but float
// math produces values just larger/smaller than an int and roundOut/In on bounds would produce
// nearly a full pixel error. One such case is where the caller has produced
// near integer CTM and uses integer crop rects that would grab an extra row/column of the
// input image when using a strict roundOut.
static constexpr float kRoundEpsilon = 1e-3f;
// Both [I]Vectors and Sk[I]Sizes are transformed as non-positioned values, i.e. go through
// mapVectors() not mapPoints().
SkIVector map_as_vector(int32_t x, int32_t y, const SkMatrix& matrix) {
SkVector v = SkVector::Make(SkIntToScalar(x), SkIntToScalar(y));
matrix.mapVectors(&v, 1);
return SkIVector::Make(SkScalarRoundToInt(v.fX), SkScalarRoundToInt(v.fY));
SkVector map_as_vector(SkScalar x, SkScalar y, const SkMatrix& matrix) {
SkVector v = SkVector::Make(x, y);
matrix.mapVectors(&v, 1);
return v;
SkRect map_rect(const SkMatrix& matrix, const SkRect& rect) {
return rect.isEmpty() ? SkRect::MakeEmpty() : matrix.mapRect(rect);
SkIRect map_rect(const SkMatrix& matrix, const SkIRect& rect) {
if (rect.isEmpty()) {
return SkIRect::MakeEmpty();
// Unfortunately, there is a range of integer values such that we have 1px precision as an int,
// but less precision as a float. This can lead to non-empty SkIRects becoming empty simply
// because of float casting. If we're already dealing with a float rect or having a float
// output, that's what we're stuck with; but if we are starting form an irect and desiring an
// SkIRect output, we go through efforts to preserve the 1px precision for simple transforms.
if (matrix.isScaleTranslate()) {
double l = (double)matrix.getScaleX()*rect.fLeft + (double)matrix.getTranslateX();
double r = (double)matrix.getScaleX()*rect.fRight + (double)matrix.getTranslateX();
double t = (double)matrix.getScaleY()*rect.fTop + (double)matrix.getTranslateY();
double b = (double)matrix.getScaleY()*rect.fBottom + (double)matrix.getTranslateY();
return {sk_double_saturate2int(sk_double_floor(std::min(l, r) + kRoundEpsilon)),
sk_double_saturate2int(sk_double_floor(std::min(t, b) + kRoundEpsilon)),
sk_double_saturate2int(sk_double_ceil(std::max(l, r) - kRoundEpsilon)),
sk_double_saturate2int(sk_double_ceil(std::max(t, b) - kRoundEpsilon))};
} else {
return skif::RoundOut(matrix.mapRect(SkRect::Make(rect)));
bool inverse_map_rect(const SkMatrix& matrix, const SkRect& rect, SkRect* out) {
if (rect.isEmpty()) {
*out = SkRect::MakeEmpty();
return true;
return SkMatrixPriv::InverseMapRect(matrix, out, rect);
bool inverse_map_rect(const SkMatrix& matrix, const SkIRect& rect, SkIRect* out) {
if (rect.isEmpty()) {
*out = SkIRect::MakeEmpty();
return true;
// This is a specialized inverse equivalent to the 1px precision preserving map_rect above.
if (matrix.isScaleTranslate()) {
// A scale-translate matrix with a 0 scale factor is not invertible.
if (matrix.getScaleX() == 0.f || matrix.getScaleY() == 0.f) {
return false;
double l = (rect.fLeft - (double)matrix.getTranslateX()) / (double)matrix.getScaleX();
double r = (rect.fRight - (double)matrix.getTranslateX()) / (double)matrix.getScaleX();
double t = (rect.fTop - (double)matrix.getTranslateY()) / (double)matrix.getScaleY();
double b = (rect.fBottom - (double)matrix.getTranslateY()) / (double)matrix.getScaleY();
*out = {sk_double_saturate2int(sk_double_floor(std::min(l, r) + kRoundEpsilon)),
sk_double_saturate2int(sk_double_floor(std::min(t, b) + kRoundEpsilon)),
sk_double_saturate2int(sk_double_ceil(std::max(l, r) - kRoundEpsilon)),
sk_double_saturate2int(sk_double_ceil(std::max(t, b) - kRoundEpsilon))};
return true;
} else {
SkRect mapped;
if (inverse_map_rect(matrix, SkRect::Make(rect), &mapped)) {
*out = skif::RoundOut(mapped);
return true;
} else {
return false;
// If m is epsilon within the form [1 0 tx], this returns true and sets out to [tx, ty]
// [0 1 ty]
// [0 0 1 ]
// TODO: Use this in decomposeCTM() (and possibly extend it to support is_nearly_scale_translate)
// to be a little more forgiving on matrix types during layer configuration.
bool is_nearly_integer_translation(const LayerSpace<SkMatrix>& m,
LayerSpace<SkIPoint>* out=nullptr) {
float tx = SkScalarRoundToScalar(sk_ieee_float_divide(m.rc(0,2), m.rc(2,2)));
float ty = SkScalarRoundToScalar(sk_ieee_float_divide(m.rc(1,2), m.rc(2,2)));
SkMatrix expected = SkMatrix::MakeAll(1.f, 0.f, tx,
0.f, 1.f, ty,
0.f, 0.f, 1.f);
for (int i = 0; i < 9; ++i) {
if (!SkScalarNearlyEqual(expected.get(i), m.get(i), kRoundEpsilon)) {
return false;
if (out) {
*out = LayerSpace<SkIPoint>({(int) tx, (int) ty});
return true;
// Assumes 'image' is decal-tiled, so everything outside the image bounds but inside dstBounds is
// transparent black, in which case the returned special image may be smaller than dstBounds.
std::pair<sk_sp<SkSpecialImage>, LayerSpace<SkIPoint>> extract_subset(
const SkSpecialImage* image,
LayerSpace<SkIPoint> origin,
const LayerSpace<SkIRect>& dstBounds) {
LayerSpace<SkIRect> imageBounds(SkIRect::MakeXYWH(origin.x(), origin.y(),
image->width(), image->height()));
if (!imageBounds.intersect(dstBounds)) {
return {nullptr, {}};
// Offset the image subset directly to avoid issues negating (origin). With the prior
// intersection (bounds - origin) will be >= 0, but (bounds + (-origin)) may not, (e.g.
// origin is INT_MIN).
SkIRect subset = { imageBounds.left() - origin.x(), - origin.y(),
imageBounds.right() - origin.x(),
imageBounds.bottom() - origin.y() };
SkASSERT(subset.fLeft >= 0 && subset.fTop >= 0 &&
subset.fRight <= image->width() && subset.fBottom <= image->height());
return {image->makeSubset(subset), imageBounds.topLeft()};
bool fills_layer_bounds(const SkColorFilter* colorFilter) {
return colorFilter && as_CFB(colorFilter)->affectsTransparentBlack();
// AutoSurface manages an SkSpecialSurface and canvas state to draw to a layer-space bounding box,
// and then snap it into a FilterResult. It provides operators to be used directly as a canvas,
// assuming surface creation succeeded. Usage:
// AutoSurface surface{ctx, dstBounds, renderInParameterSpace}; // if true, concats layer matrix
// if (surface) {
// surface->drawFoo(...);
// }
// return surface.snap(); // Automatically handles failed allocations
class AutoSurface {
AutoSurface(const Context& ctx,
const LayerSpace<SkIRect>& dstBounds,
bool renderInParameterSpace,
const SkSurfaceProps* props = nullptr)
: fSurface(nullptr)
, fDstBounds(dstBounds) {
// We don't intersect by ctx.desiredOutput() and only use the Context to make the surface.
// It is assumed the caller has already accounted for the desired output, or it's a
// situation where the desired output shouldn't apply (e.g. this surface will be transformed
// to align with the actual desired output via FilterResult metadata).
fSurface = ctx.makeSurface(SkISize(fDstBounds.size()), props);
if (!fSurface) {
// Configure the canvas
SkCanvas* canvas = fSurface->getCanvas();
// GPU-backed special surfaces don't reset their contents.
canvas->translate(-fDstBounds.left(),; // dst's origin adjustment
if (renderInParameterSpace) {
explicit operator bool() const { return SkToBool(fSurface); }
SkCanvas* canvas() { SkASSERT(fSurface); return fSurface->getCanvas(); }
SkCanvas* operator->() { SkASSERT(fSurface); return fSurface->getCanvas(); }
// NOTE: This pair is equivalent to a FilterResult but we keep it this way for use by resolve(),
// which wants them separate while the legacy imageAndOffset() function is around.
std::pair<sk_sp<SkSpecialImage>, LayerSpace<SkIPoint>> snap() {
if (fSurface) {
return {fSurface->makeImageSnapshot(), fDstBounds.topLeft()};
} else {
return {nullptr, {}};
sk_sp<SkSpecialSurface> fSurface;
LayerSpace<SkIRect> fDstBounds;
} // anonymous namespace
SkIRect RoundOut(SkRect r) { return r.makeInset(kRoundEpsilon, kRoundEpsilon).roundOut(); }
SkIRect RoundIn(SkRect r) { return r.makeOutset(kRoundEpsilon, kRoundEpsilon).roundIn(); }
sk_sp<SkSpecialSurface> Context::makeSurface(const SkISize& size,
const SkSurfaceProps* props) const {
if (!props) {
props = &fInfo.fSurfaceProps;
SkImageInfo imageInfo = SkImageInfo::Make(size,
#if defined(SK_GANESH)
if (fGaneshContext) {
// FIXME: Context should also store a surface origin that matches the source origin
return SkSpecialSurface::MakeRenderTarget(fGaneshContext,
} else
#if defined(SK_GRAPHITE)
if (fGraphiteRecorder) {
return SkSpecialSurface::MakeGraphite(fGraphiteRecorder, imageInfo, *props);
} else
return SkSpecialSurface::MakeRaster(imageInfo, *props);
// Mapping
bool Mapping::decomposeCTM(const SkMatrix& ctm, const SkImageFilter* filter,
const skif::ParameterSpace<SkPoint>& representativePt) {
SkMatrix remainder, layer;
SkSize decomposed;
using MatrixCapability = SkImageFilter_Base::MatrixCapability;
MatrixCapability capability =
filter ? as_IFB(filter)->getCTMCapability() : MatrixCapability::kComplex;
if (capability == MatrixCapability::kTranslate) {
// Apply the entire CTM post-filtering
remainder = ctm;
layer = SkMatrix::I();
} else if (ctm.isScaleTranslate() || capability == MatrixCapability::kComplex) {
// Either layer space can be anything (kComplex) - or - it can be scale+translate, and the
// ctm is. In both cases, the layer space can be equivalent to device space.
remainder = SkMatrix::I();
layer = ctm;
} else if (ctm.decomposeScale(&decomposed, &remainder)) {
// This case implies some amount of sampling post-filtering, either due to skew or rotation
// in the original matrix. As such, keep the layer matrix as simple as possible.
layer = SkMatrix::Scale(decomposed.fWidth, decomposed.fHeight);
} else {
// Perspective, which has a non-uniform scaling effect on the filter. Pick a single scale
// factor that best matches where the filter will be evaluated.
SkScalar scale = SkMatrixPriv::DifferentialAreaScale(ctm, SkPoint(representativePt));
if (SkScalarIsFinite(scale) && !SkScalarNearlyZero(scale)) {
// Now take the sqrt to go from an area scale factor to a scaling per X and Y
// FIXME: It would be nice to be able to choose a non-uniform scale.
scale = SkScalarSqrt(scale);
} else {
// The representative point was behind the W = 0 plane, so don't factor out any scale.
// NOTE: This makes remainder and layer the same as the MatrixCapability::Translate case
scale = 1.f;
remainder = ctm;
remainder.preScale(SkScalarInvert(scale), SkScalarInvert(scale));
layer = SkMatrix::Scale(scale, scale);
SkMatrix invRemainder;
if (!remainder.invert(&invRemainder)) {
// Under floating point arithmetic, it's possible to decompose an invertible matrix into
// a scaling matrix and a remainder and have the remainder be non-invertible. Generally
// when this happens the scale factors are so large and the matrix so ill-conditioned that
// it's unlikely that any drawing would be reasonable, so failing to make a layer is okay.
return false;
} else {
fParamToLayerMatrix = layer;
fLayerToDevMatrix = remainder;
fDevToLayerMatrix = invRemainder;
return true;
bool Mapping::adjustLayerSpace(const SkMatrix& layer) {
SkMatrix invLayer;
if (!layer.invert(&invLayer)) {
return false;
return true;
// Instantiate map specializations for the 6 geometric types used during filtering
SkRect Mapping::map<SkRect>(const SkRect& geom, const SkMatrix& matrix) {
return map_rect(matrix, geom);
SkIRect Mapping::map<SkIRect>(const SkIRect& geom, const SkMatrix& matrix) {
return map_rect(matrix, geom);
SkIPoint Mapping::map<SkIPoint>(const SkIPoint& geom, const SkMatrix& matrix) {
SkPoint p = SkPoint::Make(SkIntToScalar(geom.fX), SkIntToScalar(geom.fY));
matrix.mapPoints(&p, 1);
return SkIPoint::Make(SkScalarRoundToInt(p.fX), SkScalarRoundToInt(p.fY));
SkPoint Mapping::map<SkPoint>(const SkPoint& geom, const SkMatrix& matrix) {
SkPoint p;
matrix.mapPoints(&p, &geom, 1);
return p;
IVector Mapping::map<IVector>(const IVector& geom, const SkMatrix& matrix) {
return IVector(map_as_vector(geom.fX, geom.fY, matrix));
Vector Mapping::map<Vector>(const Vector& geom, const SkMatrix& matrix) {
return Vector(map_as_vector(geom.fX, geom.fY, matrix));
SkISize Mapping::map<SkISize>(const SkISize& geom, const SkMatrix& matrix) {
SkIVector v = map_as_vector(geom.fWidth, geom.fHeight, matrix);
return SkISize::Make(v.fX, v.fY);
SkSize Mapping::map<SkSize>(const SkSize& geom, const SkMatrix& matrix) {
SkVector v = map_as_vector(geom.fWidth, geom.fHeight, matrix);
return SkSize::Make(v.fX, v.fY);
SkMatrix Mapping::map<SkMatrix>(const SkMatrix& m, const SkMatrix& matrix) {
// If 'matrix' maps from the C1 coord space to the C2 coord space, and 'm' is a transform that
// operates on, and outputs to, the C1 coord space, we want to return a new matrix that is
// equivalent to 'm' that operates on and outputs to C2. This is the same as mapping the input
// from C2 to C1 (matrix^-1), then transforming by 'm', and then mapping from C1 to C2 (matrix).
SkMatrix inv;
return inv;
// LayerSpace<T>
LayerSpace<SkRect> LayerSpace<SkMatrix>::mapRect(const LayerSpace<SkRect>& r) const {
return LayerSpace<SkRect>(map_rect(fData, SkRect(r)));
LayerSpace<SkIRect> LayerSpace<SkMatrix>::mapRect(const LayerSpace<SkIRect>& r) const {
return LayerSpace<SkIRect>(map_rect(fData, SkIRect(r)));
bool LayerSpace<SkMatrix>::inverseMapRect(const LayerSpace<SkRect>& r,
LayerSpace<SkRect>* out) const {
SkRect mapped;
if (inverse_map_rect(fData, SkRect(r), &mapped)) {
*out = LayerSpace<SkRect>(mapped);
return true;
} else {
return false;
bool LayerSpace<SkMatrix>::inverseMapRect(const LayerSpace<SkIRect>& r,
LayerSpace<SkIRect>* out) const {
SkIRect mapped;
if (inverse_map_rect(fData, SkIRect(r), &mapped)) {
*out = LayerSpace<SkIRect>(mapped);
return true;
} else {
return false;
// FilterResult
sk_sp<SkSpecialImage> FilterResult::imageAndOffset(const Context& ctx, SkIPoint* offset) const {
auto [image, origin] = this->resolve(ctx, fLayerBounds);
*offset = SkIPoint(origin);
return image;
bool FilterResult::isCropped(const LayerSpace<SkMatrix>& xtraTransform,
const LayerSpace<SkIRect>& dstBounds) const {
// Tiling and color-filtering can completely fill 'fLayerBounds' in which case its edge is
// a transition from possibly non-transparent to definitely transparent color.
bool fillsLayerBounds = fills_layer_bounds(fColorFilter.get());
if (!fillsLayerBounds) {
// When that's not the case, 'fLayerBounds' may still be important if it crops the
// edges of the original transformed image itself.
LayerSpace<SkIRect> imageBounds = fTransform.mapRect(
LayerSpace<SkIRect>{SkIRect::MakeWH(fImage->width(), fImage->height())});
fillsLayerBounds = !fLayerBounds.contains(imageBounds);
if (fillsLayerBounds) {
// Some content (either the image itself, or tiling/color-filtering) can produce
// non-transparent output beyond 'fLayerBounds'. 'fLayerBounds' can only be ignored if the
// desired output is completely contained within it (i.e. the edges of 'fLayerBounds' are
// not visible).
// NOTE: For the identity transform, this is equal to !fLayerBounds.contains(dstBounds)
return !SkRectPriv::QuadContainsRect(SkMatrix(xtraTransform),
} else {
// No part of the sampled and color-filtered image would produce non-transparent pixels
// outside of 'fLayerBounds' so 'fLayerBounds' can be ignored.
return false;
FilterResult FilterResult::applyCrop(const Context& ctx,
const LayerSpace<SkIRect>& crop) const {
LayerSpace<SkIRect> tightBounds = crop;
// TODO(michaelludwig): Intersecting to the target output is only valid when the crop has
// decal tiling (the only current option).
if (!fImage ||
!tightBounds.intersect(ctx.desiredOutput()) ||
!tightBounds.intersect(fLayerBounds)) {
// The desired output would be filled with transparent black. There should never be a
// color filter acting on an empty image that could change that assumption.
SkASSERT(fImage || !fColorFilter);
return {};
LayerSpace<SkIPoint> origin;
if (!fills_layer_bounds(fColorFilter.get()) &&
is_nearly_integer_translation(fTransform, &origin)) {
// We can lift the crop to earlier in the order of operations and apply it to the image
// subset directly. This does not rely on resolve() to call extract_subset() because it
// will still render a new image if there's a color filter. As such, we have to preserve
// the current color filter on the new FilterResult.
// NOTE: Even though applying a crop never renders a new image, moving the crop into the
// image dimensions allows future operations like applying a transform or color filter to
// be composed without rendering a new image since there is no longer an intervening crop.
FilterResult restrictedOutput = extract_subset(fImage.get(), origin, tightBounds);
restrictedOutput.fColorFilter = fColorFilter;
return restrictedOutput;
} else {
// Otherwise cropping is the final operation to the FilterResult's image and can always be
// applied by adjusting the layer bounds.
FilterResult restrictedOutput = *this;
restrictedOutput.fLayerBounds = tightBounds;
return restrictedOutput;
FilterResult FilterResult::applyColorFilter(const Context& ctx,
sk_sp<SkColorFilter> colorFilter) const {
static const LayerSpace<SkMatrix> kIdentity{SkMatrix::I()};
// A null filter is the identity, so it should have been caught during image filter DAG creation
// Color filters are applied after the transform and image sampling, but before the fLayerBounds
// crop. We can compose 'colorFilter' with any previously applied color filter regardless
// of the transform/sample state, so long as it respects the effect of the current crop.
LayerSpace<SkIRect> newLayerBounds = fLayerBounds;
if (as_CFB(colorFilter)->affectsTransparentBlack()) {
if (!fImage || !newLayerBounds.intersect(ctx.desiredOutput())) {
// The current image's intersection with the desired output is fully transparent, but
// the new color filter converts that into a non-transparent color. The desired output
// is filled with this color.
// TODO: When kClamp is supported, we can allocate a smaller surface
sk_sp<SkSpecialSurface> surface = ctx.makeSurface(SkISize(ctx.desiredOutput().size()));
if (!surface) {
return {};
SkPaint paint;
paint.setColor4f(SkColors::kTransparent, /*colorSpace=*/nullptr);
return {surface->makeImageSnapshot(), ctx.desiredOutput().topLeft()};
if (this->isCropped(kIdentity, ctx.desiredOutput())) {
// Since 'colorFilter' modifies transparent black, the new result's layer bounds must
// be the desired output. But if the current image is cropped we need to resolve the
// image to avoid losing the effect of the current 'fLayerBounds'.
FilterResult filtered = this->resolve(ctx, ctx.desiredOutput());
return filtered.applyColorFilter(ctx, std::move(colorFilter));
// otherwise we can fill out to the desired output without worrying about losing the crop.
newLayerBounds = ctx.desiredOutput();
} else {
if (!fImage || !newLayerBounds.intersect(ctx.desiredOutput())) {
// The color filter does not modify transparent black, so it remains transparent
return {};
// otherwise a non-transparent affecting color filter can always be lifted before any crop
// because it does not change the "shape" of the prior FilterResult.
// If we got here we can compose the new color filter with the previous filter and the prior
// layer bounds are either soft-cropped to the desired output, or we fill out the desired output
// when the new color filter affects transparent black. We don't check if the entire composed
// filter affects transparent black because earlier floods are restricted by the layer bounds.
FilterResult filtered = *this;
filtered.fLayerBounds = newLayerBounds;
filtered.fColorFilter = SkColorFilters::Compose(std::move(colorFilter), fColorFilter);
return filtered;
static bool compatible_sampling(const SkSamplingOptions& currentSampling,
bool currentXformWontAffectNearest,
SkSamplingOptions* nextSampling,
bool nextXformWontAffectNearest) {
// Both transforms could perform non-trivial sampling, but if they are similar enough we
// assume performing one non-trivial sampling operation with the concatenated transform will
// not be visually distinguishable from sampling twice.
// TODO(michaelludwig): For now ignore mipmap policy, SkSpecialImages are not supposed to be
// drawn with mipmapping, and the majority of filter steps produce images that are at the
// proper scale and do not define mip levels. The main exception is the ::Image() filter
// leaf but that doesn't use this system yet.
if (currentSampling.isAniso() && nextSampling->isAniso()) {
// Assume we can get away with one sampling at the highest anisotropy level
*nextSampling = SkSamplingOptions::Aniso(std::max(currentSampling.maxAniso,
return true;
} else if (currentSampling.isAniso() && nextSampling->filter == SkFilterMode::kLinear) {
// Assume we can get away with the current anisotropic filter since the next is linear
*nextSampling = currentSampling;
return true;
} else if (nextSampling->isAniso() && currentSampling.filter == SkFilterMode::kLinear) {
// Mirror of the above, assume we can just get away with next's anisotropic filter
return true;
} else if (currentSampling.useCubic && (nextSampling->filter == SkFilterMode::kLinear ||
(nextSampling->useCubic &&
currentSampling.cubic.B == nextSampling->cubic.B &&
currentSampling.cubic.C == nextSampling->cubic.C))) {
// Assume we can get away with the current bicubic filter, since the next is the same
// or a bilerp that can be upgraded.
*nextSampling = currentSampling;
return true;
} else if (nextSampling->useCubic && currentSampling.filter == SkFilterMode::kLinear) {
// Mirror of the above, assume we can just get away with next's cubic resampler
return true;
} else if (currentSampling.filter == SkFilterMode::kLinear &&
nextSampling->filter == SkFilterMode::kLinear) {
// Assume we can get away with a single bilerp vs. the two
return true;
} else if (nextSampling->filter == SkFilterMode::kNearest && currentXformWontAffectNearest) {
// The next transform and nearest-neighbor filtering isn't impacted by the current transform
SkASSERT(currentSampling.filter == SkFilterMode::kLinear);
return true;
} else if (currentSampling.filter == SkFilterMode::kNearest && nextXformWontAffectNearest) {
// The next transform doesn't change the nearest-neighbor filtering of the current transform
SkASSERT(nextSampling->filter == SkFilterMode::kLinear);
*nextSampling = currentSampling;
return true;
} else {
// The current or next sampling is nearest neighbor, and will produce visible texels
// oriented with the current transform; assume this is a desired effect and preserve it.
return false;
FilterResult FilterResult::applyTransform(const Context& ctx,
const LayerSpace<SkMatrix> &transform,
const SkSamplingOptions &sampling) const {
if (!fImage) {
// Transformed transparent black remains transparent black.
return {};
// Extract the sampling options that matter based on the current and next transforms.
// We make sure the new sampling is bilerp (default) if the new transform doesn't matter
// (and assert that the current is bilerp if its transform didn't matter). Bilerp can be
// maximally combined, so simplifies the logic in compatible_sampling().
const bool currentXformIsInteger = is_nearly_integer_translation(fTransform);
const bool nextXformIsInteger = is_nearly_integer_translation(transform);
SkASSERT(!currentXformIsInteger || fSamplingOptions == kDefaultSampling);
SkSamplingOptions nextSampling = nextXformIsInteger ? kDefaultSampling : sampling;
// Determine if the image is being visibly cropped by the layer bounds, in which case we can't
// merge this transform with any previous transform (unless the new transform is an integer
// translation in which case any visible edge is aligned with the desired output and can be
// resolved by intersecting the transformed layer bounds and the output bounds).
bool isCropped = !nextXformIsInteger && this->isCropped(transform, ctx.desiredOutput());
FilterResult transformed;
if (!isCropped && compatible_sampling(fSamplingOptions, currentXformIsInteger,
&nextSampling, nextXformIsInteger)) {
// We can concat transforms and 'nextSampling' will be either fSamplingOptions,
// sampling, or a merged combination depending on the two transforms in play.
transformed = *this;
} else {
// We'll have to resolve this FilterResult first before 'transform' and 'sampling' can be
// correctly evaluated. 'nextSampling' will always be 'sampling'.
LayerSpace<SkIRect> tightBounds;
if (transform.inverseMapRect(ctx.desiredOutput(), &tightBounds)) {
transformed = this->resolve(ctx, tightBounds);
if (!transformed.fImage) {
// Transform not invertible or resolve failed to create an image
return {};
transformed.fSamplingOptions = nextSampling;
// Rebuild the layer bounds and then restrict to the current desired output. The original value
// of fLayerBounds includes the image mapped by the original fTransform as well as any
// accumulated soft crops from desired outputs of prior stages. To prevent discarding that info,
// we map fLayerBounds by the additional transform, instead of re-mapping the image bounds.
transformed.fLayerBounds = transform.mapRect(transformed.fLayerBounds);
if (!transformed.fLayerBounds.intersect(ctx.desiredOutput())) {
// The transformed output doesn't touch the desired, so it would just be transparent black.
// TODO: This intersection only applies when the tile mode is kDecal.
return {};
return transformed;
std::pair<sk_sp<SkSpecialImage>, LayerSpace<SkIPoint>> FilterResult::resolve(
const Context& ctx,
LayerSpace<SkIRect> dstBounds) const {
// The layer bounds is the final clip, so it can always be used to restrict 'dstBounds'. Even
// if there's a non-decal tile mode or transparent-black affecting color filter, those floods
// are restricted to fLayerBounds.
if (!fImage || !dstBounds.intersect(fLayerBounds)) {
return {nullptr, {}};
// If we have any extra effect to apply, there's no point in trying to extract a subset.
// TODO: Also factor in a non-decal tile mode
const bool subsetCompatible = !fColorFilter;
// TODO(michaelludwig): If we get to the point where all filter results track bounds in
// floating point, then we can extend this case to any S+T transform.
LayerSpace<SkIPoint> origin;
if (subsetCompatible && is_nearly_integer_translation(fTransform, &origin)) {
return extract_subset(fImage.get(), origin, dstBounds);
} // else fall through and attempt a draw
// Don't use context properties to avoid DMSAA on internal stages of filter evaluation.
SkSurfaceProps props = {};
AutoSurface surface{ctx, dstBounds, /*renderInParameterSpace=*/false, &props};
if (surface) {
return surface.snap();
void FilterResult::draw(SkCanvas* canvas) const {
if (!fImage) {
// When this is called by resolve(), the surface and canvas matrix are such that this clip is
// trivially a no-op, but including the clip means draw() works correctly in other scenarios.
SkPaint paint;
canvas->concat(SkMatrix(fTransform)); // src's origin is embedded in fTransform
// If we are an integer translate, the default bilinear sampling *should* be equivalent to
// nearest-neighbor. Going through the direct image-drawing path tends to detect this
// and reduce sampling automatically. When we have to use an image shader, this isn't
// detected and some GPUs' linear filtering doesn't exactly match nearest-neighbor and can
// lead to leaks beyond the image's subset. Detect and reduce sampling explicitly.
SkSamplingOptions sampling = fSamplingOptions;
if (sampling == kDefaultSampling && is_nearly_integer_translation(fTransform)) {
sampling = {};
if (fills_layer_bounds(fColorFilter.get())) {
paint.setShader(fImage->asShader(SkTileMode::kDecal, sampling, SkMatrix::I()));
} else {
fImage->draw(canvas, 0.f, 0.f, sampling, &paint);
FilterResult FilterResult::MakeFromPicture(const Context& ctx,
sk_sp<SkPicture> pic,
ParameterSpace<SkRect> cullRect) {
if (!pic) {
return {};
LayerSpace<SkIRect> dstBounds = ctx.mapping().paramToLayer(cullRect).roundOut();
if (!dstBounds.intersect(ctx.desiredOutput())) {
return {};
// Given the standard usage of the picture image filter (i.e., to render content at a fixed
// resolution that, most likely, differs from the screen's) disable LCD text by removing any
// knowledge of the pixel geometry.
// TODO: Should we just generally do this for layers with image filters? Or can we preserve it
// for layers that are still axis-aligned?
SkSurfaceProps props = ctx.surfaceProps().cloneWithPixelGeometry(kUnknown_SkPixelGeometry);
AutoSurface surface{ctx, dstBounds, /*renderInParameterSpace=*/true, &props};
if (surface) {
return surface.snap();
FilterResult FilterResult::MakeFromShader(const Context& ctx,
sk_sp<SkShader> shader,
bool dither) {
if (!shader) {
return {};
AutoSurface surface{ctx, ctx.desiredOutput(), /*renderInParameterSpace=*/true};
if (surface) {
SkPaint paint;
return surface.snap();
FilterResult FilterResult::MakeFromImage(const Context& ctx,
sk_sp<SkImage> image,
const SkRect& srcRect,
const ParameterSpace<SkRect>& dstRect,
const SkSamplingOptions& sampling) {
if (!image) {
return {};
// Check for direct conversion to an SkSpecialImage and then FilterResult. Eventually this
// whole function should be replaceable with:
// FilterResult(fImage, fSrcRect, fDstRect).applyTransform(mapping.layerMatrix(), fSampling);
SkIRect srcSubset = RoundOut(srcRect);
if (SkRect::Make(srcSubset) == srcRect) {
// Construct an SkSpecialImage from the subset directly instead of drawing.
auto specialImage = SkSpecialImage::MakeFromImage(
ctx.getContext(), srcSubset, std::move(image), ctx.surfaceProps());
// Treat the srcRect's top left as "layer" space since we are folding the src->dst transform
// and the param->layer transform into a single transform step.
skif::FilterResult subset{std::move(specialImage),
SkMatrix transform = SkMatrix::Concat(ctx.mapping().layerMatrix(),
SkMatrix::RectToRect(srcRect, SkRect(dstRect)));
return subset.applyTransform(ctx, skif::LayerSpace<SkMatrix>(transform), sampling);
// For now, draw the src->dst subset of image into a new image.
LayerSpace<SkIRect> dstBounds = ctx.mapping().paramToLayer(dstRect).roundOut();
if (!dstBounds.intersect(ctx.desiredOutput())) {
return {};
AutoSurface surface{ctx, dstBounds, /*renderInParameterSpace=*/true};
if (surface) {
SkPaint paint;
surface->drawImageRect(image, srcRect, SkRect(dstRect), sampling, &paint,
return surface.snap();
// FilterResult::Builder
LayerSpace<SkIRect> FilterResult::Builder::outputBounds() const {
// The union of all inputs' layer bounds
LayerSpace<SkIRect> output = fInputs[0].layerBounds();
for (int i = 1; i < fInputs.size(); ++i) {
// Intersect against desired output now since a Builder never has to produce an image larger
// than its context's desired output.
if (!output.intersect(fContext.desiredOutput())) {
return LayerSpace<SkIRect>::Empty();
return output;
FilterResult FilterResult::Builder::merge() {
if (fInputs.empty()) {
return {};
} else if (fInputs.size() == 1) {
return fInputs[0];
const LayerSpace<SkIRect> outputBounds = this->outputBounds();
AutoSurface surface{fContext, outputBounds, /*renderInParameterSpace=*/false};
if (surface) {
for (const FilterResult& input : fInputs) {
return surface.snap();
} // end namespace skif