blob: f9a85ffa4db41a4e55ae08f5b63353a4d126b51d [file] [log] [blame]
* Copyright 2012 The Android Open Source Project
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include "include/core/SkImageFilter.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkRect.h"
#include "include/effects/SkComposeImageFilter.h"
#include "include/private/SkSafe32.h"
#include "src/core/SkFuzzLogging.h"
#include "src/core/SkImageFilterCache.h"
#include "src/core/SkImageFilter_Base.h"
#include "src/core/SkLocalMatrixImageFilter.h"
#include "src/core/SkMatrixImageFilter.h"
#include "src/core/SkReadBuffer.h"
#include "src/core/SkSpecialImage.h"
#include "src/core/SkSpecialSurface.h"
#include "src/core/SkValidationUtils.h"
#include "src/core/SkWriteBuffer.h"
#include "include/gpu/GrContext.h"
#include "include/private/GrRecordingContext.h"
#include "src/gpu/GrColorSpaceXform.h"
#include "src/gpu/GrContextPriv.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/GrRenderTargetContext.h"
#include "src/gpu/GrTextureProxy.h"
#include "src/gpu/SkGr.h"
#include <atomic>
// SkImageFilter - A number of the public APIs on SkImageFilter downcast to SkImageFilter_Base
// in order to perform their actual work.
* Returns the number of inputs this filter will accept (some inputs can
* be NULL).
int SkImageFilter::countInputs() const { return as_IFB(this)->fInputs.count(); }
* Returns the input filter at a given index, or NULL if no input is
* connected. The indices used are filter-specific.
const SkImageFilter* SkImageFilter::getInput(int i) const {
SkASSERT(i < this->countInputs());
return as_IFB(this)->fInputs[i].get();
bool SkImageFilter::isColorFilterNode(SkColorFilter** filterPtr) const {
return as_IFB(this)->onIsColorFilterNode(filterPtr);
SkIRect SkImageFilter::filterBounds(const SkIRect& src, const SkMatrix& ctm,
MapDirection direction, const SkIRect* inputRect) const {
// The old filterBounds() function uses SkIRects that are defined in layer space so, while
// we still are supporting it, bypass SkIF_B's new public filter bounds functions and go right
// to the internal layer-space calculations.
skif::Mapping mapping(SkMatrix::I(), ctm);
if (kReverse_MapDirection == direction) {
skif::LayerSpace<SkIRect> targetOutput(src);
skif::LayerSpace<SkIRect> content(inputRect ? *inputRect : src);
return SkIRect(as_IFB(this)->onGetInputLayerBounds(mapping, targetOutput, content));
} else {
skif::LayerSpace<SkIRect> content(src);
skif::LayerSpace<SkIRect> output = as_IFB(this)->onGetOutputLayerBounds(mapping, content);
// Manually apply the crop rect for now, until cropping is performed by a dedicated SkIF.
SkIRect dst;
SkIRect(output), ctm, as_IFB(this)->affectsTransparentBlack(), &dst);
return dst;
SkRect SkImageFilter::computeFastBounds(const SkRect& src) const {
if (0 == this->countInputs()) {
return src;
SkRect combinedBounds = this->getInput(0) ? this->getInput(0)->computeFastBounds(src) : src;
for (int i = 1; i < this->countInputs(); i++) {
const SkImageFilter* input = this->getInput(i);
if (input) {
} else {
return combinedBounds;
bool SkImageFilter::canComputeFastBounds() const {
if (as_IFB(this)->affectsTransparentBlack()) {
return false;
for (int i = 0; i < this->countInputs(); i++) {
const SkImageFilter* input = this->getInput(i);
if (input && !input->canComputeFastBounds()) {
return false;
return true;
bool SkImageFilter::asAColorFilter(SkColorFilter** filterPtr) const {
SkASSERT(nullptr != filterPtr);
if (!this->isColorFilterNode(filterPtr)) {
return false;
if (nullptr != this->getInput(0) || as_CFB(*filterPtr)->affectsTransparentBlack()) {
return false;
return true;
sk_sp<SkImageFilter> SkImageFilter::MakeMatrixFilter(const SkMatrix& matrix,
SkFilterQuality filterQuality,
sk_sp<SkImageFilter> input) {
return SkMatrixImageFilter::Make(matrix, filterQuality, std::move(input));
sk_sp<SkImageFilter> SkImageFilter::makeWithLocalMatrix(const SkMatrix& matrix) const {
return SkLocalMatrixImageFilter::Make(matrix, this->refMe());
// SkImageFilter_Base
static int32_t next_image_filter_unique_id() {
static std::atomic<int32_t> nextID{1};
int32_t id;
do {
id = nextID++;
} while (id == 0);
return id;
SkImageFilter_Base::SkImageFilter_Base(sk_sp<SkImageFilter> const* inputs,
int inputCount, const CropRect* cropRect)
: fUsesSrcInput(false)
, fUniqueID(next_image_filter_unique_id()) {
fCropRect = cropRect ? *cropRect : CropRect(SkRect(), 0x0);
for (int i = 0; i < inputCount; ++i) {
if (!inputs[i] || as_IFB(inputs[i])->fUsesSrcInput) {
fUsesSrcInput = true;
fInputs[i] = inputs[i];
SkImageFilter_Base::~SkImageFilter_Base() {
bool SkImageFilter_Base::Common::unflatten(SkReadBuffer& buffer, int expectedCount) {
const int count = buffer.readInt();
if (!buffer.validate(count >= 0)) {
return false;
if (!buffer.validate(expectedCount < 0 || count == expectedCount)) {
return false;
for (int i = 0; i < count; i++) {
fInputs.push_back(buffer.readBool() ? buffer.readImageFilter() : nullptr);
if (!buffer.isValid()) {
return false;
SkRect rect;
if (!buffer.isValid() || !buffer.validate(SkIsValidRect(rect))) {
return false;
uint32_t flags = buffer.readUInt();
fCropRect = CropRect(rect, flags);
return buffer.isValid();
void SkImageFilter_Base::flatten(SkWriteBuffer& buffer) const {
for (int i = 0; i < fInputs.count(); i++) {
const SkImageFilter* input = this->getInput(i);
buffer.writeBool(input != nullptr);
if (input != nullptr) {
skif::FilterResult<For::kOutput> SkImageFilter_Base::filterImage(const skif::Context& context) const {
// TODO (michaelludwig) - Old filters have an implicit assumption that the source image
// (originally passed separately) has an origin of (0, 0). SkComposeImageFilter makes an effort
// to ensure that remains the case. Once everyone uses the new type systems for bounds, non
// (0, 0) source origins will be easy to support.
SkASSERT(context.source().layerOrigin().x() == 0 && context.source().layerOrigin().y() == 0);
skif::FilterResult<For::kOutput> result;
if (!context.isValid()) {
return result;
uint32_t srcGenID = fUsesSrcInput ? context.sourceImage()->uniqueID() : 0;
const SkIRect srcSubset = fUsesSrcInput ? context.sourceImage()->subset()
: SkIRect::MakeWH(0, 0);
SkImageFilterCacheKey key(fUniqueID, context.mapping().layerMatrix(), context.clipBounds(),
srcGenID, srcSubset);
if (context.cache() && context.cache()->get(key, &result)) {
return result;
result = this->onFilterImage(context);
if (context.gpuBacked()) {
SkASSERT(!result.image() || result.image()->isTextureBacked());
if (context.cache()) {
context.cache()->set(key, this, result);
return result;
skif::LayerSpace<SkIRect> SkImageFilter_Base::getInputBounds(
const skif::Mapping& mapping, const skif::DeviceSpace<SkRect>& desiredOutput,
const skif::ParameterSpace<SkRect>* knownContentBounds) const {
// Map both the device-space desired coverage area and the known content bounds to layer space
skif::LayerSpace<SkIRect> desiredBounds = mapping.deviceToLayer(desiredOutput).roundOut();
// If we have no known content bounds use the desired coverage area, because that is the most
// conservative possibility.
skif::LayerSpace<SkIRect> contentBounds =
knownContentBounds ? mapping.paramToLayer(*knownContentBounds).roundOut()
: desiredBounds;
// Process the layer-space desired output with the filter DAG to determine required input
skif::LayerSpace<SkIRect> requiredInput = this->onGetInputLayerBounds(
mapping, desiredBounds, contentBounds);
// If we know what's actually going to be drawn into the layer, and we don't change transparent
// black, then we can further restrict the layer to what the known content is
if (knownContentBounds && !this->affectsTransparentBlack()) {
if (!requiredInput.intersect(contentBounds)) {
// Nothing would be output by the filter, so return empty rect
return skif::LayerSpace<SkIRect>(SkIRect::MakeEmpty());
return requiredInput;
skif::DeviceSpace<SkIRect> SkImageFilter_Base::getOutputBounds(
const skif::Mapping& mapping, const skif::ParameterSpace<SkRect>& contentBounds) const {
// Map the input content into the layer space where filtering will occur
skif::LayerSpace<SkRect> layerContent = mapping.paramToLayer(contentBounds);
// Determine the filter DAGs output bounds in layer space
skif::LayerSpace<SkIRect> filterOutput = this->onGetOutputLayerBounds(
mapping, layerContent.roundOut());
// FIXME (michaelludwig) - To be removed once cropping is isolated, but remain consistent with
// old filterBounds(kForward) behavior.
SkIRect dst;
SkIRect(filterOutput), mapping.layerMatrix(),
as_IFB(this)->affectsTransparentBlack(), &dst);
// Map all the way to device space
return mapping.layerToDevice(skif::LayerSpace<SkIRect>(dst));
// TODO (michaelludwig) - Default to using the old onFilterImage, as filters are updated one by one.
// Once the old function is gone, this onFilterImage() will be made a pure virtual.
skif::FilterResult<For::kOutput> SkImageFilter_Base::onFilterImage(const skif::Context& context) const {
SkIPoint origin;
auto image = this->onFilterImage(context, &origin);
return skif::FilterResult<For::kOutput>(std::move(image), skif::LayerSpace<SkIPoint>(origin));
bool SkImageFilter_Base::canHandleComplexCTM() const {
// CropRects need to apply in the source coordinate system, but are not aware of complex CTMs
// when performing clipping. For a simple fix, any filter with a crop rect set cannot support
// complex CTMs until that's updated.
if (this->cropRectIsSet() || !this->onCanHandleComplexCTM()) {
return false;
const int count = this->countInputs();
for (int i = 0; i < count; ++i) {
const SkImageFilter_Base* input = as_IFB(this->getInput(i));
if (input && !input->canHandleComplexCTM()) {
return false;
return true;
void SkImageFilter::CropRect::applyTo(const SkIRect& imageBounds, const SkMatrix& ctm,
bool embiggen, SkIRect* cropped) const {
*cropped = imageBounds;
if (fFlags) {
SkRect devCropR;
ctm.mapRect(&devCropR, fRect);
SkIRect devICropR = devCropR.roundOut();
// Compute the left/top first, in case we need to modify the right/bottom for a missing edge
if (fFlags & kHasLeft_CropEdge) {
if (embiggen || devICropR.fLeft > cropped->fLeft) {
cropped->fLeft = devICropR.fLeft;
} else {
devICropR.fRight = Sk32_sat_add(cropped->fLeft, devICropR.width());
if (fFlags & kHasTop_CropEdge) {
if (embiggen || devICropR.fTop > cropped->fTop) {
cropped->fTop = devICropR.fTop;
} else {
devICropR.fBottom = Sk32_sat_add(cropped->fTop, devICropR.height());
if (fFlags & kHasWidth_CropEdge) {
if (embiggen || devICropR.fRight < cropped->fRight) {
cropped->fRight = devICropR.fRight;
if (fFlags & kHasHeight_CropEdge) {
if (embiggen || devICropR.fBottom < cropped->fBottom) {
cropped->fBottom = devICropR.fBottom;
bool SkImageFilter_Base::applyCropRect(const Context& ctx, const SkIRect& srcBounds,
SkIRect* dstBounds) const {
SkIRect tmpDst = this->onFilterNodeBounds(srcBounds, ctx.ctm(), kForward_MapDirection, nullptr);
fCropRect.applyTo(tmpDst, ctx.ctm(), this->affectsTransparentBlack(), dstBounds);
// Intersect against the clip bounds, in case the crop rect has
// grown the bounds beyond the original clip. This can happen for
// example in tiling, where the clip is much smaller than the filtered
// primitive. If we didn't do this, we would be processing the filter
// at the full crop rect size in every tile.
return dstBounds->intersect(ctx.clipBounds());
// Return a larger (newWidth x newHeight) copy of 'src' with black padding
// around it.
static sk_sp<SkSpecialImage> pad_image(SkSpecialImage* src, const SkImageFilter_Base::Context& ctx,
int newWidth, int newHeight, int offX, int offY) {
// We would like to operate in the source's color space (so that we return an "identical"
// image, other than the padding. To achieve that, we'd create a new context using
// src->getColorSpace() to replace ctx.colorSpace().
// That fails in at least two ways. For formats that are texturable but not renderable (like
// F16 on some ES implementations), we can't create a surface to do the work. For sRGB, images
// may be tagged with an sRGB color space (which leads to an sRGB config in makeSurface). But
// the actual config of that sRGB image on a device with no sRGB support is non-sRGB.
// Rather than try to special case these situations, we execute the image padding in the
// destination color space. This should not affect the output of the DAG in (almost) any case,
// because the result of this call is going to be used as an input, where it would have been
// switched to the destination space anyway. The one exception would be a filter that expected
// to consume unclamped F16 data, but the padded version of the image is pre-clamped to 8888.
// We can revisit this logic if that ever becomes an actual problem.
sk_sp<SkSpecialSurface> surf(ctx.makeSurface(SkISize::Make(newWidth, newHeight)));
if (!surf) {
return nullptr;
SkCanvas* canvas = surf->getCanvas();
src->draw(canvas, offX, offY, nullptr);
return surf->makeImageSnapshot();
sk_sp<SkSpecialImage> SkImageFilter_Base::applyCropRectAndPad(const Context& ctx,
SkSpecialImage* src,
SkIPoint* srcOffset,
SkIRect* bounds) const {
const SkIRect srcBounds = SkIRect::MakeXYWH(srcOffset->x(), srcOffset->y(),
src->width(), src->height());
if (!this->applyCropRect(ctx, srcBounds, bounds)) {
return nullptr;
if (srcBounds.contains(*bounds)) {
return sk_sp<SkSpecialImage>(SkRef(src));
} else {
sk_sp<SkSpecialImage> img(pad_image(src, ctx, bounds->width(), bounds->height(),
Sk32_sat_sub(srcOffset->x(), bounds->x()),
Sk32_sat_sub(srcOffset->y(), bounds->y())));
*srcOffset = SkIPoint::Make(bounds->x(), bounds->y());
return img;
// NOTE: The new onGetOutputLayerBounds() and onGetInputLayerBounds() default to calling into the
// deprecated onFilterBounds and onFilterNodeBounds. While these functions are not tagged, they do
// match the documented default behavior for the new bounds functions.
SkIRect SkImageFilter_Base::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
MapDirection dir, const SkIRect* inputRect) const {
if (this->countInputs() < 1) {
return src;
SkIRect totalBounds;
for (int i = 0; i < this->countInputs(); ++i) {
const SkImageFilter* filter = this->getInput(i);
SkIRect rect = filter ? filter->filterBounds(src, ctm, dir, inputRect) : src;
if (0 == i) {
totalBounds = rect;
} else {
return totalBounds;
SkIRect SkImageFilter_Base::onFilterNodeBounds(const SkIRect& src, const SkMatrix&,
MapDirection, const SkIRect*) const {
return src;
skif::LayerSpace<SkIRect> SkImageFilter_Base::visitInputLayerBounds(
const skif::Mapping& mapping, const skif::LayerSpace<SkIRect>& desiredOutput,
const skif::LayerSpace<SkIRect>& contentBounds) const {
if (this->countInputs() < 1) {
// TODO (michaelludwig) - if a filter doesn't have any inputs, it doesn't need any
// implicit source image, so arguably we could return an empty rect here. 'desiredOutput' is
// consistent with original behavior, so empty bounds may have unintended side effects
// but should be explored later.
return desiredOutput;
skif::LayerSpace<SkIRect> netInput;
for (int i = 0; i < this->countInputs(); ++i) {
const SkImageFilter* filter = this->getInput(i);
// The required input for this input filter, or 'targetOutput' if the filter is null and
// the source image is used (so must be sized to cover 'targetOutput').
skif::LayerSpace<SkIRect> requiredInput =
filter ? as_IFB(filter)->onGetInputLayerBounds(mapping, desiredOutput,
: desiredOutput;
// Accumulate with all other filters
if (i == 0) {
netInput = requiredInput;
} else {
return netInput;
skif::LayerSpace<SkIRect> SkImageFilter_Base::visitOutputLayerBounds(
const skif::Mapping& mapping, const skif::LayerSpace<SkIRect>& contentBounds) const {
if (this->countInputs() < 1) {
// TODO (michaelludwig) - if a filter doesn't have any inputs, it presumably is determining
// its output size from something other than the implicit source contentBounds, in which
// case it shouldn't be calling this helper function, so explore adding an unreachable test
return contentBounds;
skif::LayerSpace<SkIRect> netOutput;
for (int i = 0; i < this->countInputs(); ++i) {
const SkImageFilter* filter = this->getInput(i);
// The output for just this input filter, or 'contentBounds' if the filter is null and
// the source image is used (i.e. the identity filter applied to the source).
skif::LayerSpace<SkIRect> output =
filter ? as_IFB(filter)->onGetOutputLayerBounds(mapping, contentBounds)
: contentBounds;
// Accumulate with all other filters
if (i == 0) {
netOutput = output;
} else {
return netOutput;
skif::LayerSpace<SkIRect> SkImageFilter_Base::onGetInputLayerBounds(
const skif::Mapping& mapping, const skif::LayerSpace<SkIRect>& desiredOutput,
const skif::LayerSpace<SkIRect>& contentBounds, VisitChildren recurse) const {
// Call old functions for now since they may have been overridden by a subclass that's not been
// updated yet; normally this would just default to visitInputLayerBounds()
SkIRect content = SkIRect(contentBounds);
SkIRect input = this->onFilterNodeBounds(SkIRect(desiredOutput), mapping.layerMatrix(),
kReverse_MapDirection, &content);
if (recurse == VisitChildren::kYes) {
SkIRect aggregate = this->onFilterBounds(input, mapping.layerMatrix(),
kReverse_MapDirection, &input);
return skif::LayerSpace<SkIRect>(aggregate);
} else {
return skif::LayerSpace<SkIRect>(input);
skif::LayerSpace<SkIRect> SkImageFilter_Base::onGetOutputLayerBounds(
const skif::Mapping& mapping, const skif::LayerSpace<SkIRect>& contentBounds) const {
// Call old functions for now; normally this would default to visitOutputLayerBounds()
SkIRect aggregate = this->onFilterBounds(SkIRect(contentBounds), mapping.layerMatrix(),
kForward_MapDirection, nullptr);
SkIRect output = this->onFilterNodeBounds(aggregate, mapping.layerMatrix(),
kForward_MapDirection, nullptr);
return skif::LayerSpace<SkIRect>(output);
template<skif::Usage kU>
skif::FilterResult<kU> SkImageFilter_Base::filterInput(int index, const skif::Context& ctx) const {
// Sanity checks for the index-specific input usages
SkASSERT(kU != skif::Usage::kInput0 || index == 0);
SkASSERT(kU != skif::Usage::kInput1 || index == 1);
const SkImageFilter* input = this->getInput(index);
if (!input) {
// Convert from the generic kInput of the source image to kU
return static_cast<skif::FilterResult<kU>>(ctx.source());
skif::FilterResult<For::kOutput> result = as_IFB(input)->filterImage(this->mapContext(ctx));
SkASSERT(!result.image() || ctx.gpuBacked() == result.image()->isTextureBacked());
// Map the output result of the input image filter to the input usage requested for this filter
return static_cast<skif::FilterResult<kU>>(std::move(result));
// Instantiate filterInput() for kInput, kInput0, and kInput1. This does not provide a definition
// for kOutput, which should never be used anyways, and this way the linker will fail for us then.
template skif::FilterResult<For::kInput> SkImageFilter_Base::filterInput(int, const skif::Context&) const;
template skif::FilterResult<For::kInput0> SkImageFilter_Base::filterInput(int, const skif::Context&) const;
template skif::FilterResult<For::kInput1> SkImageFilter_Base::filterInput(int, const skif::Context&) const;
SkImageFilter_Base::Context SkImageFilter_Base::mapContext(const Context& ctx) const {
// We don't recurse through the child input filters because that happens automatically
// as part of the filterImage() evaluation. In this case, we want the bounds for the
// edge from this node to its children, without the effects of the child filters.
skif::LayerSpace<SkIRect> childOutput = this->onGetInputLayerBounds(
ctx.mapping(), ctx.desiredOutput(), ctx.desiredOutput(), VisitChildren::kNo);
return ctx.withNewDesiredOutput(childOutput);
sk_sp<SkSpecialImage> SkImageFilter_Base::DrawWithFP(GrRecordingContext* context,
std::unique_ptr<GrFragmentProcessor> fp,
const SkIRect& bounds,
SkColorType colorType,
const SkColorSpace* colorSpace,
GrProtected isProtected) {
GrPaint paint;
auto renderTargetContext = GrRenderTargetContext::Make(
context, SkColorTypeToGrColorType(colorType), sk_ref_sp(colorSpace),
SkBackingFit::kApprox, bounds.size(), 1, GrMipMapped::kNo, isProtected,
if (!renderTargetContext) {
return nullptr;
SkIRect dstIRect = SkIRect::MakeWH(bounds.width(), bounds.height());
SkRect srcRect = SkRect::Make(bounds);
SkRect dstRect = SkRect::MakeWH(srcRect.width(), srcRect.height());
renderTargetContext->fillRectToRect(nullptr, std::move(paint), GrAA::kNo, SkMatrix::I(),
dstRect, srcRect);
return SkSpecialImage::MakeDeferredFromGpu(
context, dstIRect, kNeedNewImageUniqueID_SpecialImage,
renderTargetContext->readSurfaceView(), renderTargetContext->colorInfo().colorType(),
sk_sp<SkSpecialImage> SkImageFilter_Base::ImageToColorSpace(SkSpecialImage* src,
SkColorType colorType,
SkColorSpace* colorSpace) {
// There are several conditions that determine if we actually need to convert the source to the
// destination's color space. Rather than duplicate that logic here, just try to make an xform
// object. If that produces something, then both are tagged, and the source is in a different
// gamut than the dest. There is some overhead to making the xform, but those are cached, and
// if we get one back, that means we're about to use it during the conversion anyway.
auto colorSpaceXform = GrColorSpaceXform::Make(src->getColorSpace(), src->alphaType(),
colorSpace, kPremul_SkAlphaType);
if (!colorSpaceXform) {
// No xform needed, just return the original image
return sk_ref_sp(src);
sk_sp<SkSpecialSurface> surf(src->makeSurface(colorType, colorSpace,
SkISize::Make(src->width(), src->height())));
if (!surf) {
return sk_ref_sp(src);
SkCanvas* canvas = surf->getCanvas();
SkPaint p;
src->draw(canvas, 0, 0, &p);
return surf->makeImageSnapshot();
// In repeat mode, when we are going to sample off one edge of the srcBounds we require the
// opposite side be preserved.
SkIRect SkImageFilter_Base::DetermineRepeatedSrcBound(const SkIRect& srcBounds,
const SkIVector& filterOffset,
const SkISize& filterSize,
const SkIRect& originalSrcBounds) {
SkIRect tmp = srcBounds;
tmp.adjust(-filterOffset.fX, -filterOffset.fY,
filterSize.fWidth - filterOffset.fX, filterSize.fHeight - filterOffset.fY);
if (tmp.fLeft < originalSrcBounds.fLeft || tmp.fRight > originalSrcBounds.fRight) {
tmp.fLeft = originalSrcBounds.fLeft;
tmp.fRight = originalSrcBounds.fRight;
if (tmp.fTop < originalSrcBounds.fTop || tmp.fBottom > originalSrcBounds.fBottom) {
tmp.fTop = originalSrcBounds.fTop;
tmp.fBottom = originalSrcBounds.fBottom;
return tmp;
void SkImageFilter_Base::PurgeCache() {
static sk_sp<SkImageFilter> apply_ctm_to_filter(sk_sp<SkImageFilter> input, const SkMatrix& ctm,
SkMatrix* remainder) {
if (ctm.isScaleTranslate() || as_IFB(input)->canHandleComplexCTM()) {
// The filter supports the CTM, so leave it as-is and 'remainder' stores the whole CTM
*remainder = ctm;
return input;
// We have a complex CTM and a filter that can't support them, so it needs to use the matrix
// transform filter that resamples the image contents. Decompose the simple portion of the ctm
// into 'remainder'
SkMatrix ctmToEmbed;
SkSize scale;
if (ctm.decomposeScale(&scale, &ctmToEmbed)) {
// decomposeScale splits ctm into scale * ctmToEmbed, so bake ctmToEmbed into DAG
// with a matrix filter and return scale as the remaining matrix for the real CTM.
remainder->setScale(scale.fWidth, scale.fHeight);
// ctmToEmbed is passed to SkMatrixImageFilter, which performs its transforms as if it were
// a pre-transformation before applying the image-filter context's CTM. In this case, we
// need ctmToEmbed to be a post-transformation (i.e. after the scale matrix since
// decomposeScale produces ctm = ctmToEmbed * scale). Giving scale^-1 * ctmToEmbed * scale
// to the matrix filter achieves this effect.
// TODO (michaelludwig) - When the original root node of a filter can be drawn directly to a
// device using ctmToEmbed, this abuse of SkMatrixImageFilter can go away.
ctmToEmbed.preScale(scale.fWidth, scale.fHeight);
ctmToEmbed.postScale(1.f / scale.fWidth, 1.f / scale.fHeight);
} else {
// Unable to decompose
// FIXME Ideally we'd embed the entire CTM as part of the matrix image filter, but
// the device <-> src bounds calculations for filters are very brittle under perspective,
// and can easily run into precision issues (wrong bounds that clip), or performance issues
// (producing large source-space images where 80% of the image is compressed into a few
// device pixels). A longer term solution for perspective-space image filtering is needed
// see
if (ctm.hasPerspective()) {
*remainder = ctm;
return input;
ctmToEmbed = ctm;
return SkMatrixImageFilter::Make(ctmToEmbed, kLow_SkFilterQuality, input);
sk_sp<SkImageFilter> SkImageFilter_Base::applyCTM(const SkMatrix& ctm, SkMatrix* remainder) const {
return apply_ctm_to_filter(this->refMe(), ctm, remainder);