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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/**
* DownscalingSurfaceFilter is a SurfaceFilter implementation for use with
* SurfacePipe which performs Lanczos downscaling.
*
* It's in this header file, separated from the other SurfaceFilters, because
* some preprocessor magic is necessary to ensure that there aren't compilation
* issues on platforms where Skia is unavailable.
*/
#ifndef mozilla_image_DownscalingFilter_h
#define mozilla_image_DownscalingFilter_h
#include <algorithm>
#include <ctime>
#include <stdint.h>
#include "mozilla/Maybe.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/ConvolutionFilter.h"
#include "SurfacePipe.h"
namespace mozilla {
namespace image {
//////////////////////////////////////////////////////////////////////////////
// DownscalingFilter
//////////////////////////////////////////////////////////////////////////////
template <typename Next>
class DownscalingFilter;
/**
* A configuration struct for DownscalingConfig.
*/
struct DownscalingConfig {
template <typename Next>
using Filter = DownscalingFilter<Next>;
gfx::IntSize mInputSize; /// The size of the input image. We'll downscale
/// from this size to the input size of the next
/// SurfaceFilter in the chain.
gfx::SurfaceFormat mFormat; /// The pixel format - BGRA or BGRX. (BGRX has
/// slightly better performance.)
};
/**
* DownscalingFilter performs Lanczos downscaling, taking image input data at
* one size and outputting it rescaled to a different size.
*
* The 'Next' template parameter specifies the next filter in the chain.
*/
template <typename Next>
class DownscalingFilter final : public SurfaceFilter {
public:
DownscalingFilter()
: mWindowCapacity(0),
mRowsInWindow(0),
mInputRow(0),
mOutputRow(0),
mHasAlpha(true) {}
~DownscalingFilter() { ReleaseWindow(); }
template <typename... Rest>
nsresult Configure(const DownscalingConfig& aConfig, const Rest&... aRest) {
nsresult rv = mNext.Configure(aRest...);
if (NS_FAILED(rv)) {
return rv;
}
if (mNext.InputSize() == aConfig.mInputSize) {
NS_WARNING("Created a downscaler, but not downscaling?");
return NS_ERROR_INVALID_ARG;
}
if (mNext.InputSize().width > aConfig.mInputSize.width) {
NS_WARNING("Created a downscaler, but width is larger");
return NS_ERROR_INVALID_ARG;
}
if (mNext.InputSize().height > aConfig.mInputSize.height) {
NS_WARNING("Created a downscaler, but height is larger");
return NS_ERROR_INVALID_ARG;
}
if (aConfig.mInputSize.width <= 0 || aConfig.mInputSize.height <= 0) {
NS_WARNING("Invalid input size for DownscalingFilter");
return NS_ERROR_INVALID_ARG;
}
mInputSize = aConfig.mInputSize;
gfx::IntSize outputSize = mNext.InputSize();
mScale =
gfx::MatrixScalesDouble(double(mInputSize.width) / outputSize.width,
double(mInputSize.height) / outputSize.height);
mHasAlpha = aConfig.mFormat == gfx::SurfaceFormat::OS_RGBA;
ReleaseWindow();
auto resizeMethod = gfx::ConvolutionFilter::ResizeMethod::LANCZOS3;
if (!mXFilter.ComputeResizeFilter(resizeMethod, mInputSize.width,
outputSize.width) ||
!mYFilter.ComputeResizeFilter(resizeMethod, mInputSize.height,
outputSize.height)) {
NS_WARNING("Failed to compute filters for image downscaling");
return NS_ERROR_OUT_OF_MEMORY;
}
// Allocate the buffer, which contains scanlines of the input image.
mRowBuffer.reset(new (fallible)
uint8_t[PaddedWidthInBytes(mInputSize.width)]);
if (MOZ_UNLIKELY(!mRowBuffer)) {
return NS_ERROR_OUT_OF_MEMORY;
}
// Clear the buffer to avoid writing uninitialized memory to the output.
memset(mRowBuffer.get(), 0, PaddedWidthInBytes(mInputSize.width));
// Allocate the window, which contains horizontally downscaled scanlines.
// (We can store scanlines which are already downscaled because our
// downscaling filter is separable.)
mWindowCapacity = mYFilter.MaxFilter();
mWindow.reset(new (fallible) uint8_t*[mWindowCapacity]);
if (MOZ_UNLIKELY(!mWindow)) {
return NS_ERROR_OUT_OF_MEMORY;
}
// Allocate the "window" of recent rows that we keep in memory as input for
// the downscaling code. We intentionally iterate through the entire array
// even if an allocation fails, to ensure that all the pointers in it are
// either valid or nullptr. That in turn ensures that ReleaseWindow() can
// clean up correctly.
bool anyAllocationFailed = false;
const size_t windowRowSizeInBytes = PaddedWidthInBytes(outputSize.width);
for (int32_t i = 0; i < mWindowCapacity; ++i) {
mWindow[i] = new (fallible) uint8_t[windowRowSizeInBytes];
anyAllocationFailed = anyAllocationFailed || mWindow[i] == nullptr;
}
if (MOZ_UNLIKELY(anyAllocationFailed)) {
return NS_ERROR_OUT_OF_MEMORY;
}
ConfigureFilter(mInputSize, sizeof(uint32_t));
return NS_OK;
}
Maybe<SurfaceInvalidRect> TakeInvalidRect() override {
Maybe<SurfaceInvalidRect> invalidRect = mNext.TakeInvalidRect();
if (invalidRect) {
// Compute the input space invalid rect by scaling.
invalidRect->mInputSpaceRect.ScaleRoundOut(mScale.xScale, mScale.yScale);
}
return invalidRect;
}
protected:
uint8_t* DoResetToFirstRow() override {
mNext.ResetToFirstRow();
mInputRow = 0;
mOutputRow = 0;
mRowsInWindow = 0;
return GetRowPointer();
}
uint8_t* DoAdvanceRowFromBuffer(const uint8_t* aInputRow) override {
if (mInputRow >= mInputSize.height) {
NS_WARNING("Advancing DownscalingFilter past the end of the input");
return nullptr;
}
if (mOutputRow >= mNext.InputSize().height) {
NS_WARNING("Advancing DownscalingFilter past the end of the output");
return nullptr;
}
int32_t filterOffset = 0;
int32_t filterLength = 0;
mYFilter.GetFilterOffsetAndLength(mOutputRow, &filterOffset, &filterLength);
int32_t inputRowToRead = filterOffset + mRowsInWindow;
MOZ_ASSERT(mInputRow <= inputRowToRead, "Reading past end of input");
if (mInputRow == inputRowToRead) {
MOZ_RELEASE_ASSERT(mRowsInWindow < mWindowCapacity,
"Need more rows than capacity!");
mXFilter.ConvolveHorizontally(aInputRow, mWindow[mRowsInWindow++],
mHasAlpha);
}
MOZ_ASSERT(mOutputRow < mNext.InputSize().height,
"Writing past end of output");
while (mRowsInWindow >= filterLength) {
DownscaleInputRow();
if (mOutputRow == mNext.InputSize().height) {
break; // We're done.
}
mYFilter.GetFilterOffsetAndLength(mOutputRow, &filterOffset,
&filterLength);
}
mInputRow++;
return mInputRow < mInputSize.height ? GetRowPointer() : nullptr;
}
uint8_t* DoAdvanceRow() override {
return DoAdvanceRowFromBuffer(mRowBuffer.get());
}
private:
uint8_t* GetRowPointer() const { return mRowBuffer.get(); }
static size_t PaddedWidthInBytes(size_t aLogicalWidth) {
// Convert from width in BGRA/BGRX pixels to width in bytes, padding
// to handle overreads by the SIMD code inside Skia.
return gfx::ConvolutionFilter::PadBytesForSIMD(aLogicalWidth *
sizeof(uint32_t));
}
void DownscaleInputRow() {
MOZ_ASSERT(mOutputRow < mNext.InputSize().height,
"Writing past end of output");
int32_t filterOffset = 0;
int32_t filterLength = 0;
mYFilter.GetFilterOffsetAndLength(mOutputRow, &filterOffset, &filterLength);
mNext.template WriteUnsafeComputedRow<uint32_t>([&](uint32_t* aRow,
uint32_t aLength) {
mYFilter.ConvolveVertically(mWindow.get(),
reinterpret_cast<uint8_t*>(aRow), mOutputRow,
mXFilter.NumValues(), mHasAlpha);
});
mOutputRow++;
if (mOutputRow == mNext.InputSize().height) {
return; // We're done.
}
int32_t newFilterOffset = 0;
int32_t newFilterLength = 0;
mYFilter.GetFilterOffsetAndLength(mOutputRow, &newFilterOffset,
&newFilterLength);
int diff = newFilterOffset - filterOffset;
MOZ_ASSERT(diff >= 0, "Moving backwards in the filter?");
// Shift the buffer. We're just moving pointers here, so this is cheap.
mRowsInWindow -= diff;
mRowsInWindow = std::clamp(mRowsInWindow, 0, mWindowCapacity);
// If we already have enough rows to satisfy the filter, there is no need
// to swap as we won't be writing more before the next convolution.
if (filterLength > mRowsInWindow) {
for (int32_t i = 0; i < mRowsInWindow; ++i) {
std::swap(mWindow[i], mWindow[filterLength - mRowsInWindow + i]);
}
}
}
void ReleaseWindow() {
if (!mWindow) {
return;
}
for (int32_t i = 0; i < mWindowCapacity; ++i) {
delete[] mWindow[i];
}
mWindow = nullptr;
mWindowCapacity = 0;
}
Next mNext; /// The next SurfaceFilter in the chain.
gfx::IntSize mInputSize; /// The size of the input image.
gfx::MatrixScalesDouble mScale; /// The scale factors in each dimension.
/// Computed from @mInputSize and
/// the next filter's input size.
UniquePtr<uint8_t[]> mRowBuffer; /// The buffer into which input is written.
UniquePtr<uint8_t*[]> mWindow; /// The last few rows which were written.
gfx::ConvolutionFilter mXFilter; /// The Lanczos filter in X.
gfx::ConvolutionFilter mYFilter; /// The Lanczos filter in Y.
int32_t mWindowCapacity; /// How many rows the window contains.
int32_t mRowsInWindow; /// How many rows we've buffered in the window.
int32_t mInputRow; /// The current row we're reading. (0-indexed)
int32_t mOutputRow; /// The current row we're writing. (0-indexed)
bool mHasAlpha; /// If true, the image has transparency.
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_DownscalingFilter_h