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gecko-dev/image/SurfaceFilters.h

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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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* This header contains various SurfaceFilter implementations that apply
* transformations to image data, for usage with SurfacePipe.
*/
#ifndef mozilla_image_SurfaceFilters_h
#define mozilla_image_SurfaceFilters_h
#include <algorithm>
#include <stdint.h>
#include <string.h>
#include "mozilla/Likely.h"
#include "mozilla/Maybe.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/gfx/2D.h"
#include "DownscalingFilter.h"
#include "SurfaceCache.h"
#include "SurfacePipe.h"
namespace mozilla {
namespace image {
//////////////////////////////////////////////////////////////////////////////
// DeinterlacingFilter
//////////////////////////////////////////////////////////////////////////////
template <typename PixelType, typename Next> class DeinterlacingFilter;
/**
* A configuration struct for DeinterlacingFilter.
*
* The 'PixelType' template parameter should be either uint32_t (for output to a
* SurfaceSink) or uint8_t (for output to a PalettedSurfaceSink).
*/
template <typename PixelType>
struct DeinterlacingConfig
{
template <typename Next> using Filter = DeinterlacingFilter<PixelType, Next>;
bool mProgressiveDisplay; /// If true, duplicate rows during deinterlacing
/// to make progressive display look better, at
/// the cost of some performance.
};
/**
* DeinterlacingFilter performs deinterlacing by reordering the rows that are
* written to it.
*
* The 'PixelType' template parameter should be either uint32_t (for output to a
* SurfaceSink) or uint8_t (for output to a PalettedSurfaceSink).
*
* The 'Next' template parameter specifies the next filter in the chain.
*/
template <typename PixelType, typename Next>
class DeinterlacingFilter final : public SurfaceFilter
{
public:
DeinterlacingFilter()
: mInputRow(0)
, mOutputRow(0)
, mPass(0)
, mProgressiveDisplay(true)
{ }
template <typename... Rest>
nsresult Configure(const DeinterlacingConfig<PixelType>& aConfig, const Rest&... aRest)
{
nsresult rv = mNext.Configure(aRest...);
if (NS_FAILED(rv)) {
return rv;
}
if (sizeof(PixelType) == 1 && !mNext.IsValidPalettedPipe()) {
NS_WARNING("Paletted DeinterlacingFilter used with non-paletted pipe?");
return NS_ERROR_INVALID_ARG;
}
if (sizeof(PixelType) == 4 && mNext.IsValidPalettedPipe()) {
NS_WARNING("Non-paletted DeinterlacingFilter used with paletted pipe?");
return NS_ERROR_INVALID_ARG;
}
gfx::IntSize outputSize = mNext.InputSize();
mProgressiveDisplay = aConfig.mProgressiveDisplay;
const uint32_t bufferSize = outputSize.width *
outputSize.height *
sizeof(PixelType);
// Use the size of the SurfaceCache as a heuristic to avoid gigantic
// allocations. Even if DownscalingFilter allowed us to allocate space for
// the output image, the deinterlacing buffer may still be too big, and
// fallible allocation won't always save us in the presence of overcommit.
if (!SurfaceCache::CanHold(bufferSize)) {
return NS_ERROR_OUT_OF_MEMORY;
}
// Allocate the buffer, which contains deinterlaced scanlines of the image.
// The buffer is necessary so that we can output rows which have already
// been deinterlaced again on subsequent passes. Since a later stage in the
// pipeline may be transforming the rows it receives (for example, by
// downscaling them), the rows may no longer exist in their original form on
// the surface itself.
mBuffer.reset(new (fallible) uint8_t[bufferSize]);
if (MOZ_UNLIKELY(!mBuffer)) {
return NS_ERROR_OUT_OF_MEMORY;
}
// Clear the buffer to avoid writing uninitialized memory to the output.
memset(mBuffer.get(), 0, bufferSize);
ConfigureFilter(outputSize, sizeof(PixelType));
return NS_OK;
}
bool IsValidPalettedPipe() const override
{
return sizeof(PixelType) == 1 && mNext.IsValidPalettedPipe();
}
Maybe<SurfaceInvalidRect> TakeInvalidRect() override
{
return mNext.TakeInvalidRect();
}
protected:
uint8_t* DoResetToFirstRow() override
{
mNext.ResetToFirstRow();
mPass = 0;
mInputRow = 0;
mOutputRow = InterlaceOffset(mPass);
return GetRowPointer(mOutputRow);
}
uint8_t* DoAdvanceRow() override
{
if (mPass >= 4) {
return nullptr; // We already finished all passes.
}
if (mInputRow >= InputSize().height) {
return nullptr; // We already got all the input rows we expect.
}
// Duplicate from the first Haeberli row to the remaining Haeberli rows
// within the buffer.
DuplicateRows(HaeberliOutputStartRow(mPass, mProgressiveDisplay, mOutputRow),
HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), mOutputRow));
// Write the current set of Haeberli rows (which contains the current row)
// to the next stage in the pipeline.
OutputRows(HaeberliOutputStartRow(mPass, mProgressiveDisplay, mOutputRow),
HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), mOutputRow));
// Determine which output row the next input row corresponds to.
bool advancedPass = false;
uint32_t stride = InterlaceStride(mPass);
int32_t nextOutputRow = mOutputRow + stride;
while (nextOutputRow >= InputSize().height) {
// Copy any remaining rows from the buffer.
if (!advancedPass) {
OutputRows(HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), mOutputRow),
InputSize().height);
}
// We finished the current pass; advance to the next one.
mPass++;
if (mPass >= 4) {
return nullptr; // Finished all passes.
}
// Tell the next pipeline stage that we're starting the next pass.
mNext.ResetToFirstRow();
// Update our state to reflect the pass change.
advancedPass = true;
stride = InterlaceStride(mPass);
nextOutputRow = InterlaceOffset(mPass);
}
MOZ_ASSERT(nextOutputRow >= 0);
MOZ_ASSERT(nextOutputRow < InputSize().height);
MOZ_ASSERT(HaeberliOutputStartRow(mPass, mProgressiveDisplay,
nextOutputRow) >= 0);
MOZ_ASSERT(HaeberliOutputStartRow(mPass, mProgressiveDisplay,
nextOutputRow) < InputSize().height);
MOZ_ASSERT(HaeberliOutputStartRow(mPass, mProgressiveDisplay,
nextOutputRow) <= nextOutputRow);
MOZ_ASSERT(HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), nextOutputRow) >= 0);
MOZ_ASSERT(HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), nextOutputRow)
<= InputSize().height);
MOZ_ASSERT(HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), nextOutputRow)
> nextOutputRow);
int32_t nextHaeberliOutputRow =
HaeberliOutputStartRow(mPass, mProgressiveDisplay, nextOutputRow);
// Copy rows from the buffer until we reach the desired output row.
if (advancedPass) {
OutputRows(0, nextHaeberliOutputRow);
} else {
OutputRows(HaeberliOutputUntilRow(mPass, mProgressiveDisplay,
InputSize(), mOutputRow),
nextHaeberliOutputRow);
}
// Update our position within the buffer.
mInputRow++;
mOutputRow = nextOutputRow;
// We'll actually write to the first Haeberli output row, then copy it until
// we reach the last Haeberli output row. The assertions above make sure
// this always includes mOutputRow.
return GetRowPointer(nextHaeberliOutputRow);
}
private:
static uint32_t InterlaceOffset(uint32_t aPass)
{
MOZ_ASSERT(aPass < 4, "Invalid pass");
static const uint8_t offset[] = { 0, 4, 2, 1 };
return offset[aPass];
}
static uint32_t InterlaceStride(uint32_t aPass)
{
MOZ_ASSERT(aPass < 4, "Invalid pass");
static const uint8_t stride[] = { 8, 8, 4, 2 };
return stride[aPass];
}
static int32_t HaeberliOutputStartRow(uint32_t aPass,
bool aProgressiveDisplay,
int32_t aOutputRow)
{
MOZ_ASSERT(aPass < 4, "Invalid pass");
static const uint8_t firstRowOffset[] = { 3, 1, 0, 0 };
if (aProgressiveDisplay) {
return std::max(aOutputRow - firstRowOffset[aPass], 0);
} else {
return aOutputRow;
}
}
static int32_t HaeberliOutputUntilRow(uint32_t aPass,
bool aProgressiveDisplay,
const gfx::IntSize& aInputSize,
int32_t aOutputRow)
{
MOZ_ASSERT(aPass < 4, "Invalid pass");
static const uint8_t lastRowOffset[] = { 4, 2, 1, 0 };
if (aProgressiveDisplay) {
return std::min(aOutputRow + lastRowOffset[aPass],
aInputSize.height - 1)
+ 1; // Add one because this is an open interval on the right.
} else {
return aOutputRow + 1;
}
}
void DuplicateRows(int32_t aStart, int32_t aUntil)
{
MOZ_ASSERT(aStart >= 0);
MOZ_ASSERT(aUntil >= 0);
if (aUntil <= aStart || aStart >= InputSize().height) {
return;
}
// The source row is the first row in the range.
const uint8_t* sourceRowPointer = GetRowPointer(aStart);
// We duplicate the source row into each subsequent row in the range.
for (int32_t destRow = aStart + 1 ; destRow < aUntil ; ++destRow) {
uint8_t* destRowPointer = GetRowPointer(destRow);
memcpy(destRowPointer, sourceRowPointer, InputSize().width * sizeof(PixelType));
}
}
void OutputRows(int32_t aStart, int32_t aUntil)
{
MOZ_ASSERT(aStart >= 0);
MOZ_ASSERT(aUntil >= 0);
if (aUntil <= aStart || aStart >= InputSize().height) {
return;
}
for (int32_t rowToOutput = aStart; rowToOutput < aUntil; ++rowToOutput) {
mNext.WriteBuffer(reinterpret_cast<PixelType*>(GetRowPointer(rowToOutput)));
}
}
uint8_t* GetRowPointer(uint32_t aRow) const
{
uint32_t offset = aRow * InputSize().width * sizeof(PixelType);
MOZ_ASSERT(offset < InputSize().width * InputSize().height * sizeof(PixelType),
"Start of row is outside of image");
MOZ_ASSERT(offset + InputSize().width * sizeof(PixelType)
<= InputSize().width * InputSize().height * sizeof(PixelType),
"End of row is outside of image");
return mBuffer.get() + offset;
}
Next mNext; /// The next SurfaceFilter in the chain.
UniquePtr<uint8_t[]> mBuffer; /// The buffer used to store reordered rows.
int32_t mInputRow; /// The current row we're reading. (0-indexed)
int32_t mOutputRow; /// The current row we're writing. (0-indexed)
uint8_t mPass; /// Which pass we're on. (0-indexed)
bool mProgressiveDisplay; /// If true, duplicate rows to optimize for
/// progressive display.
};
//////////////////////////////////////////////////////////////////////////////
// RemoveFrameRectFilter
//////////////////////////////////////////////////////////////////////////////
template <typename Next> class RemoveFrameRectFilter;
/**
* A configuration struct for RemoveFrameRectFilter.
*/
struct RemoveFrameRectConfig
{
template <typename Next> using Filter = RemoveFrameRectFilter<Next>;
gfx::IntRect mFrameRect; /// The surface subrect which contains data.
};
/**
* RemoveFrameRectFilter turns an image with a frame rect that does not match
* its logical size into an image with no frame rect. It does this by writing
* transparent pixels into any padding regions and throwing away excess data.
*
* The 'Next' template parameter specifies the next filter in the chain.
*/
template <typename Next>
class RemoveFrameRectFilter final : public SurfaceFilter
{
public:
RemoveFrameRectFilter()
: mRow(0)
{ }
template <typename... Rest>
nsresult Configure(const RemoveFrameRectConfig& aConfig, const Rest&... aRest)
{
nsresult rv = mNext.Configure(aRest...);
if (NS_FAILED(rv)) {
return rv;
}
if (mNext.IsValidPalettedPipe()) {
NS_WARNING("RemoveFrameRectFilter used with paletted pipe?");
return NS_ERROR_INVALID_ARG;
}
mFrameRect = mUnclampedFrameRect = aConfig.mFrameRect;
gfx::IntSize outputSize = mNext.InputSize();
// Forbid frame rects with negative size.
if (aConfig.mFrameRect.Width() < 0 || aConfig.mFrameRect.Height() < 0) {
return NS_ERROR_INVALID_ARG;
}
// Clamp mFrameRect to the output size.
gfx::IntRect outputRect(0, 0, outputSize.width, outputSize.height);
mFrameRect = mFrameRect.Intersect(outputRect);
// If there's no intersection, |mFrameRect| will be an empty rect positioned
// at the maximum of |inputRect|'s and |aFrameRect|'s coordinates, which is
// not what we want. Force it to (0, 0) in that case.
if (mFrameRect.IsEmpty()) {
mFrameRect.MoveTo(0, 0);
}
// We don't need an intermediate buffer unless the unclamped frame rect
// width is larger than the clamped frame rect width. In that case, the
// caller will end up writing data that won't end up in the final image at
// all, and we'll need a buffer to give that data a place to go.
if (mFrameRect.Width() < mUnclampedFrameRect.Width()) {
mBuffer.reset(new (fallible) uint8_t[mUnclampedFrameRect.Width() *
sizeof(uint32_t)]);
if (MOZ_UNLIKELY(!mBuffer)) {
return NS_ERROR_OUT_OF_MEMORY;
}
memset(mBuffer.get(), 0, mUnclampedFrameRect.Width() * sizeof(uint32_t));
}
ConfigureFilter(mUnclampedFrameRect.Size(), sizeof(uint32_t));
return NS_OK;
}
Maybe<SurfaceInvalidRect> TakeInvalidRect() override
{
return mNext.TakeInvalidRect();
}
protected:
uint8_t* DoResetToFirstRow() override
{
uint8_t* rowPtr = mNext.ResetToFirstRow();
if (rowPtr == nullptr) {
mRow = mFrameRect.YMost();
return nullptr;
}
mRow = mUnclampedFrameRect.Y();
// Advance the next pipeline stage to the beginning of the frame rect,
// outputting blank rows.
if (mFrameRect.Y() > 0) {
for (int32_t rowToOutput = 0; rowToOutput < mFrameRect.Y() ; ++rowToOutput) {
mNext.WriteEmptyRow();
}
}
// We're at the beginning of the frame rect now, so return if we're either
// ready for input or we're already done.
rowPtr = mBuffer ? mBuffer.get() : mNext.CurrentRowPointer();
if (!mFrameRect.IsEmpty() || rowPtr == nullptr) {
// Note that the pointer we're returning is for the next row we're
// actually going to write to, but we may discard writes before that point
// if mRow < mFrameRect.y.
return AdjustRowPointer(rowPtr);
}
// We've finished the region specified by the frame rect, but the frame rect
// is empty, so we need to output the rest of the image immediately. Advance
// to the end of the next pipeline stage's buffer, outputting blank rows.
while (mNext.WriteEmptyRow() == WriteState::NEED_MORE_DATA) { }
mRow = mFrameRect.YMost();
return nullptr; // We're done.
}
uint8_t* DoAdvanceRow() override
{
uint8_t* rowPtr = nullptr;
const int32_t currentRow = mRow;
mRow++;
if (currentRow < mFrameRect.Y()) {
// This row is outside of the frame rect, so just drop it on the floor.
rowPtr = mBuffer ? mBuffer.get() : mNext.CurrentRowPointer();
return AdjustRowPointer(rowPtr);
} else if (currentRow >= mFrameRect.YMost()) {
NS_WARNING("RemoveFrameRectFilter: Advancing past end of frame rect");
return nullptr;
}
// If we had to buffer, copy the data. Otherwise, just advance the row.
if (mBuffer) {
// We write from the beginning of the buffer unless |mUnclampedFrameRect.x|
// is negative; if that's the case, we have to skip the portion of the
// unclamped frame rect that's outside the row.
uint32_t* source = reinterpret_cast<uint32_t*>(mBuffer.get()) -
std::min(mUnclampedFrameRect.X(), 0);
// We write |mFrameRect.width| columns starting at |mFrameRect.x|; we've
// already clamped these values to the size of the output, so we don't
// have to worry about bounds checking here (though WriteBuffer() will do
// it for us in any case).
WriteState state = mNext.WriteBuffer(source, mFrameRect.X(), mFrameRect.Width());
rowPtr = state == WriteState::NEED_MORE_DATA ? mBuffer.get()
: nullptr;
} else {
rowPtr = mNext.AdvanceRow();
}
// If there's still more data coming or we're already done, just adjust the
// pointer and return.
if (mRow < mFrameRect.YMost() || rowPtr == nullptr) {
return AdjustRowPointer(rowPtr);
}
// We've finished the region specified by the frame rect. Advance to the end
// of the next pipeline stage's buffer, outputting blank rows.
while (mNext.WriteEmptyRow() == WriteState::NEED_MORE_DATA) { }
mRow = mFrameRect.YMost();
return nullptr; // We're done.
}
private:
uint8_t* AdjustRowPointer(uint8_t* aNextRowPointer) const
{
if (mBuffer) {
MOZ_ASSERT(aNextRowPointer == mBuffer.get() || aNextRowPointer == nullptr);
return aNextRowPointer; // No adjustment needed for an intermediate buffer.
}
if (mFrameRect.IsEmpty() ||
mRow >= mFrameRect.YMost() ||
aNextRowPointer == nullptr) {
return nullptr; // Nothing left to write.
}
return aNextRowPointer + mFrameRect.X() * sizeof(uint32_t);
}
Next mNext; /// The next SurfaceFilter in the chain.
gfx::IntRect mFrameRect; /// The surface subrect which contains data,
/// clamped to the image size.
gfx::IntRect mUnclampedFrameRect; /// The frame rect before clamping.
UniquePtr<uint8_t[]> mBuffer; /// The intermediate buffer, if one is
/// necessary because the frame rect width
/// is larger than the image's logical width.
int32_t mRow; /// The row in unclamped frame rect space
/// that we're currently writing.
};
//////////////////////////////////////////////////////////////////////////////
// ADAM7InterpolatingFilter
//////////////////////////////////////////////////////////////////////////////
template <typename Next> class ADAM7InterpolatingFilter;
/**
* A configuration struct for ADAM7InterpolatingFilter.
*/
struct ADAM7InterpolatingConfig
{
template <typename Next> using Filter = ADAM7InterpolatingFilter<Next>;
};
/**
* ADAM7InterpolatingFilter performs bilinear interpolation over an ADAM7
* interlaced image.
*
* ADAM7 breaks up the image into 8x8 blocks. On each of the 7 passes, a new set
* of pixels in each block receives their final values, according to the
* following pattern:
*
* 1 6 4 6 2 6 4 6
* 7 7 7 7 7 7 7 7
* 5 6 5 6 5 6 5 6
* 7 7 7 7 7 7 7 7
* 3 6 4 6 3 6 4 6
* 7 7 7 7 7 7 7 7
* 5 6 5 6 5 6 5 6
* 7 7 7 7 7 7 7 7
*
* When rendering the pixels that have not yet received their final values, we
* can get much better intermediate results if we interpolate between
* the pixels we *have* gotten so far. This filter performs bilinear
* interpolation by first performing linear interpolation horizontally for each
* "important" row (which we'll define as a row that has received any pixels
* with final values at all) and then performing linear interpolation vertically
* to produce pixel values for rows which aren't important on the current pass.
*
* Note that this filter totally ignores the data which is written to rows which
* aren't important on the current pass! It's fine to write nothing at all for
* these rows, although doing so won't cause any harm.
*
* XXX(seth): In bug 1280552 we'll add a SIMD implementation for this filter.
*
* The 'Next' template parameter specifies the next filter in the chain.
*/
template <typename Next>
class ADAM7InterpolatingFilter final : public SurfaceFilter
{
public:
ADAM7InterpolatingFilter()
: mPass(0) // The current pass, in the range 1..7. Starts at 0 so that
// DoResetToFirstRow() doesn't have to special case the first pass.
, mRow(0)
{ }
template <typename... Rest>
nsresult Configure(const ADAM7InterpolatingConfig& aConfig, const Rest&... aRest)
{
nsresult rv = mNext.Configure(aRest...);
if (NS_FAILED(rv)) {
return rv;
}
if (mNext.IsValidPalettedPipe()) {
NS_WARNING("ADAM7InterpolatingFilter used with paletted pipe?");
return NS_ERROR_INVALID_ARG;
}
// We have two intermediate buffers, one for the previous row with final
// pixel values and one for the row that the previous filter in the chain is
// currently writing to.
size_t inputWidthInBytes = mNext.InputSize().width * sizeof(uint32_t);
mPreviousRow.reset(new (fallible) uint8_t[inputWidthInBytes]);
if (MOZ_UNLIKELY(!mPreviousRow)) {
return NS_ERROR_OUT_OF_MEMORY;
}
mCurrentRow.reset(new (fallible) uint8_t[inputWidthInBytes]);
if (MOZ_UNLIKELY(!mCurrentRow)) {
return NS_ERROR_OUT_OF_MEMORY;
}
memset(mPreviousRow.get(), 0, inputWidthInBytes);
memset(mCurrentRow.get(), 0, inputWidthInBytes);
ConfigureFilter(mNext.InputSize(), sizeof(uint32_t));
return NS_OK;
}
Maybe<SurfaceInvalidRect> TakeInvalidRect() override
{
return mNext.TakeInvalidRect();
}
protected:
uint8_t* DoResetToFirstRow() override
{
mRow = 0;
mPass = std::min(mPass + 1, 7);
uint8_t* rowPtr = mNext.ResetToFirstRow();
if (mPass == 7) {
// Short circuit this filter on the final pass, since all pixels have
// their final values at that point.
return rowPtr;
}
return mCurrentRow.get();
}
uint8_t* DoAdvanceRow() override
{
MOZ_ASSERT(0 < mPass && mPass <= 7, "Invalid pass");
int32_t currentRow = mRow;
++mRow;
if (mPass == 7) {
// On the final pass we short circuit this filter totally.
return mNext.AdvanceRow();
}
const int32_t lastImportantRow = LastImportantRow(InputSize().height, mPass);
if (currentRow > lastImportantRow) {
return nullptr; // This pass is already complete.
}
if (!IsImportantRow(currentRow, mPass)) {
// We just ignore whatever the caller gives us for these rows. We'll
// interpolate them in later.
return mCurrentRow.get();
}
// This is an important row. We need to perform horizontal interpolation for
// these rows.
InterpolateHorizontally(mCurrentRow.get(), InputSize().width, mPass);
// Interpolate vertically between the previous important row and the current
// important row. We skip this if the current row is 0 (which is always an
// important row), because in that case there is no previous important row
// to interpolate with.
if (currentRow != 0) {
InterpolateVertically(mPreviousRow.get(), mCurrentRow.get(), mPass, mNext);
}
// Write out the current row itself, which, being an important row, does not
// need vertical interpolation.
uint32_t* currentRowAsPixels = reinterpret_cast<uint32_t*>(mCurrentRow.get());
mNext.WriteBuffer(currentRowAsPixels);
if (currentRow == lastImportantRow) {
// This is the last important row, which completes this pass. Note that
// for very small images, this may be the first row! Since there won't be
// another important row, there's nothing to interpolate with vertically,
// so we just duplicate this row until the end of the image.
while (mNext.WriteBuffer(currentRowAsPixels) == WriteState::NEED_MORE_DATA) { }
// All of the remaining rows in the image were determined above, so we're done.
return nullptr;
}
// The current row is now the previous important row; save it.
Swap(mPreviousRow, mCurrentRow);
MOZ_ASSERT(mRow < InputSize().height, "Reached the end of the surface without "
"hitting the last important row?");
return mCurrentRow.get();
}
private:
static void InterpolateVertically(uint8_t* aPreviousRow,
uint8_t* aCurrentRow,
uint8_t aPass,
SurfaceFilter& aNext)
{
const float* weights = InterpolationWeights(ImportantRowStride(aPass));
// We need to interpolate vertically to generate the rows between the
// previous important row and the next one. Recall that important rows are
// rows which contain at least some final pixels; see
// InterpolateHorizontally() for some additional explanation as to what that
// means. Note that we've already written out the previous important row, so
// we start the iteration at 1.
for (int32_t outRow = 1; outRow < ImportantRowStride(aPass); ++outRow) {
const float weight = weights[outRow];
// We iterate through the previous and current important row every time we
// write out an interpolated row, so we need to copy the pointers.
uint8_t* prevRowBytes = aPreviousRow;
uint8_t* currRowBytes = aCurrentRow;
// Write out the interpolated pixels. Interpolation is componentwise.
aNext.template WritePixelsToRow<uint32_t>([&]{
uint32_t pixel = 0;
auto* component = reinterpret_cast<uint8_t*>(&pixel);
*component++ = InterpolateByte(*prevRowBytes++, *currRowBytes++, weight);
*component++ = InterpolateByte(*prevRowBytes++, *currRowBytes++, weight);
*component++ = InterpolateByte(*prevRowBytes++, *currRowBytes++, weight);
*component++ = InterpolateByte(*prevRowBytes++, *currRowBytes++, weight);
return AsVariant(pixel);
});
}
}
static void InterpolateHorizontally(uint8_t* aRow, int32_t aWidth, uint8_t aPass)
{
// Collect the data we'll need to perform horizontal interpolation. The
// terminology here bears some explanation: a "final pixel" is a pixel which
// has received its final value. On each pass, a new set of pixels receives
// their final value; see the diagram above of the 8x8 pattern that ADAM7
// uses. Any pixel which hasn't received its final value on this pass
// derives its value from either horizontal or vertical interpolation
// instead.
const size_t finalPixelStride = FinalPixelStride(aPass);
const size_t finalPixelStrideBytes = finalPixelStride * sizeof(uint32_t);
const size_t lastFinalPixel = LastFinalPixel(aWidth, aPass);
const size_t lastFinalPixelBytes = lastFinalPixel * sizeof(uint32_t);
const float* weights = InterpolationWeights(finalPixelStride);
// Interpolate blocks of pixels which lie between two final pixels.
// Horizontal interpolation is done in place, as we'll need the results
// later when we vertically interpolate.
for (size_t blockBytes = 0;
blockBytes < lastFinalPixelBytes;
blockBytes += finalPixelStrideBytes) {
uint8_t* finalPixelA = aRow + blockBytes;
uint8_t* finalPixelB = aRow + blockBytes + finalPixelStrideBytes;
MOZ_ASSERT(finalPixelA < aRow + aWidth * sizeof(uint32_t),
"Running off end of buffer");
MOZ_ASSERT(finalPixelB < aRow + aWidth * sizeof(uint32_t),
"Running off end of buffer");
// Interpolate the individual pixels componentwise. Note that we start
// iteration at 1 since we don't need to apply any interpolation to the
// first pixel in the block, which has its final value.
for (size_t pixelIndex = 1; pixelIndex < finalPixelStride; ++pixelIndex) {
const float weight = weights[pixelIndex];
uint8_t* pixel = aRow + blockBytes + pixelIndex * sizeof(uint32_t);
MOZ_ASSERT(pixel < aRow + aWidth * sizeof(uint32_t), "Running off end of buffer");
for (size_t component = 0; component < sizeof(uint32_t); ++component) {
pixel[component] =
InterpolateByte(finalPixelA[component], finalPixelB[component], weight);
}
}
}
// For the pixels after the last final pixel in the row, there isn't a
// second final pixel to interpolate with, so just duplicate.
uint32_t* rowPixels = reinterpret_cast<uint32_t*>(aRow);
uint32_t pixelToDuplicate = rowPixels[lastFinalPixel];
for (int32_t pixelIndex = lastFinalPixel + 1;
pixelIndex < aWidth;
++pixelIndex) {
MOZ_ASSERT(pixelIndex < aWidth, "Running off end of buffer");
rowPixels[pixelIndex] = pixelToDuplicate;
}
}
static uint8_t InterpolateByte(uint8_t aByteA, uint8_t aByteB, float aWeight)
{
return uint8_t(aByteA * aWeight + aByteB * (1.0f - aWeight));
}
static int32_t ImportantRowStride(uint8_t aPass)
{
MOZ_ASSERT(0 < aPass && aPass <= 7, "Invalid pass");
// The stride between important rows for each pass, with a dummy value for
// the nonexistent pass 0.
static int32_t strides[] = { 1, 8, 8, 4, 4, 2, 2, 1 };
return strides[aPass];
}
static bool IsImportantRow(int32_t aRow, uint8_t aPass)
{
MOZ_ASSERT(aRow >= 0);
// Whether the row is important comes down to divisibility by the stride for
// this pass, which is always a power of 2, so we can check using a mask.
int32_t mask = ImportantRowStride(aPass) - 1;
return (aRow & mask) == 0;
}
static int32_t LastImportantRow(int32_t aHeight, uint8_t aPass)
{
MOZ_ASSERT(aHeight > 0);
// We can find the last important row using the same mask trick as above.
int32_t lastRow = aHeight - 1;
int32_t mask = ImportantRowStride(aPass) - 1;
return lastRow - (lastRow & mask);
}
static size_t FinalPixelStride(uint8_t aPass)
{
MOZ_ASSERT(0 < aPass && aPass <= 7, "Invalid pass");
// The stride between the final pixels in important rows for each pass, with
// a dummy value for the nonexistent pass 0.
static size_t strides[] = { 1, 8, 4, 4, 2, 2, 1, 1 };
return strides[aPass];
}
static size_t LastFinalPixel(int32_t aWidth, uint8_t aPass)
{
MOZ_ASSERT(aWidth >= 0);
// Again, we can use the mask trick above to find the last important pixel.
int32_t lastColumn = aWidth - 1;
size_t mask = FinalPixelStride(aPass) - 1;
return lastColumn - (lastColumn & mask);
}
static const float* InterpolationWeights(int32_t aStride)
{
// Precalculated interpolation weights. These are used to interpolate
// between final pixels or between important rows. Although no interpolation
// is actually applied to the previous final pixel or important row value,
// the arrays still start with 1.0f, which is always skipped, primarily
// because otherwise |stride1Weights| would have zero elements.
static float stride8Weights[] =
{ 1.0f, 7 / 8.0f, 6 / 8.0f, 5 / 8.0f, 4 / 8.0f, 3 / 8.0f, 2 / 8.0f, 1 / 8.0f };
static float stride4Weights[] = { 1.0f, 3 / 4.0f, 2 / 4.0f, 1 / 4.0f };
static float stride2Weights[] = { 1.0f, 1 / 2.0f };
static float stride1Weights[] = { 1.0f };
switch (aStride) {
case 8: return stride8Weights;
case 4: return stride4Weights;
case 2: return stride2Weights;
case 1: return stride1Weights;
default: MOZ_CRASH();
}
}
Next mNext; /// The next SurfaceFilter in the chain.
UniquePtr<uint8_t[]> mPreviousRow; /// The last important row (i.e., row with
/// final pixel values) that got written to.
UniquePtr<uint8_t[]> mCurrentRow; /// The row that's being written to right
/// now.
uint8_t mPass; /// Which ADAM7 pass we're on. Valid passes
/// are 1..7 during processing and 0 prior
/// to configuraiton.
int32_t mRow; /// The row we're currently reading.
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_SurfaceFilters_h
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