image/Downscaler.cpp
author Kartikaya Gupta <kgupta@mozilla.com>
Thu, 15 Mar 2018 15:25:09 -0400
changeset 408344 a27ceb86fbd002b8aafd2f6377c315c11254af0c
parent 403113 4afd35f217c1bc90ecdd6b010d564852a59c5eca
child 410235 52c14d32d9812951c12d92b2594056fc15c5de80
permissions -rw-r--r--
Bug 1445662 - Remove ProcessTouchVelocity from PAPZCTreeManager.ipdl. r=rhunt This function is never actually called over IPDL. It is called directly on the concrete APZCTreeManager instance by the AndroidDynamicToolbarAnimator code, both of which live in the compositor. So we don't need to expose this method on IAPZCTreeManager or over PAPZCTreeManager.

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * 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/. */

#include "Downscaler.h"

#include <algorithm>
#include <ctime>
#include "gfxPrefs.h"
#include "mozilla/gfx/2D.h"

using std::max;
using std::swap;

namespace mozilla {

using gfx::IntRect;

namespace image {

Downscaler::Downscaler(const nsIntSize& aTargetSize)
  : mTargetSize(aTargetSize)
  , mOutputBuffer(nullptr)
  , mWindowCapacity(0)
  , mHasAlpha(true)
  , mFlipVertically(false)
{
  MOZ_ASSERT(mTargetSize.width > 0 && mTargetSize.height > 0,
             "Invalid target size");
}

Downscaler::~Downscaler()
{
  ReleaseWindow();
}

void
Downscaler::ReleaseWindow()
{
  if (!mWindow) {
    return;
  }

  for (int32_t i = 0; i < mWindowCapacity; ++i) {
    delete[] mWindow[i];
  }

  mWindow = nullptr;
  mWindowCapacity = 0;
}

nsresult
Downscaler::BeginFrame(const nsIntSize& aOriginalSize,
                       const Maybe<nsIntRect>& aFrameRect,
                       uint8_t* aOutputBuffer,
                       bool aHasAlpha,
                       bool aFlipVertically /* = false */)
{
  MOZ_ASSERT(aOutputBuffer);
  MOZ_ASSERT(mTargetSize != aOriginalSize,
             "Created a downscaler, but not downscaling?");
  MOZ_ASSERT(mTargetSize.width <= aOriginalSize.width,
             "Created a downscaler, but width is larger");
  MOZ_ASSERT(mTargetSize.height <= aOriginalSize.height,
             "Created a downscaler, but height is larger");
  MOZ_ASSERT(aOriginalSize.width > 0 && aOriginalSize.height > 0,
             "Invalid original size");

  // Only downscale from reasonable sizes to avoid using too much memory/cpu
  // downscaling and decoding. 1 << 20 == 1,048,576 seems a reasonable limit.
  if (aOriginalSize.width > (1 << 20) || aOriginalSize.height > (1 << 20)) {
    NS_WARNING("Trying to downscale image frame that is too large");
    return NS_ERROR_INVALID_ARG;
  }

  mFrameRect = aFrameRect.valueOr(nsIntRect(nsIntPoint(), aOriginalSize));
  MOZ_ASSERT(mFrameRect.X() >= 0 && mFrameRect.Y() >= 0 &&
             mFrameRect.Width() >= 0 && mFrameRect.Height() >= 0,
             "Frame rect must have non-negative components");
  MOZ_ASSERT(nsIntRect(0, 0, aOriginalSize.width, aOriginalSize.height)
               .Contains(mFrameRect),
             "Frame rect must fit inside image");
  MOZ_ASSERT_IF(!nsIntRect(0, 0, aOriginalSize.width, aOriginalSize.height)
                  .IsEqualEdges(mFrameRect),
                aHasAlpha);

  mOriginalSize = aOriginalSize;
  mScale = gfxSize(double(mOriginalSize.width) / mTargetSize.width,
                   double(mOriginalSize.height) / mTargetSize.height);
  mOutputBuffer = aOutputBuffer;
  mHasAlpha = aHasAlpha;
  mFlipVertically = aFlipVertically;

  ReleaseWindow();

  auto resizeMethod = gfx::ConvolutionFilter::ResizeMethod::LANCZOS3;
  if (!mXFilter.ComputeResizeFilter(resizeMethod, mOriginalSize.width, mTargetSize.width) ||
      !mYFilter.ComputeResizeFilter(resizeMethod, mOriginalSize.height, mTargetSize.height)) {
    NS_WARNING("Failed to compute filters for image downscaling");
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // Allocate the buffer, which contains scanlines of the original image.
  // pad to handle overreads by the simd code
  size_t bufferLen = gfx::ConvolutionFilter::PadBytesForSIMD(mOriginalSize.width * sizeof(uint32_t));
  mRowBuffer.reset(new (fallible) uint8_t[bufferLen]);
  if (MOZ_UNLIKELY(!mRowBuffer)) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  // Zero buffer to keep valgrind happy.
  memset(mRowBuffer.get(), 0, bufferLen);

  // Allocate the window, which contains horizontally downscaled scanlines. (We
  // can store scanlines which are already downscale 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;
  }

  bool anyAllocationFailed = false;
  // pad to handle overreads by the simd code
  const size_t rowSize = gfx::ConvolutionFilter::PadBytesForSIMD(mTargetSize.width * sizeof(uint32_t));
  for (int32_t i = 0; i < mWindowCapacity; ++i) {
    mWindow[i] = new (fallible) uint8_t[rowSize];
    anyAllocationFailed = anyAllocationFailed || mWindow[i] == nullptr;
  }

  if (MOZ_UNLIKELY(anyAllocationFailed)) {
    // 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.
    return NS_ERROR_OUT_OF_MEMORY;
  }

  ResetForNextProgressivePass();

  return NS_OK;
}

void
Downscaler::SkipToRow(int32_t aRow)
{
  if (mCurrentInLine < aRow) {
    ClearRow();
    do {
      CommitRow();
    } while (mCurrentInLine < aRow);
  }
}

void
Downscaler::ResetForNextProgressivePass()
{
  mPrevInvalidatedLine = 0;
  mCurrentOutLine = 0;
  mCurrentInLine = 0;
  mLinesInBuffer = 0;

  if (mFrameRect.IsEmpty()) {
    // Our frame rect is zero size; commit rows until the end of the image.
    SkipToRow(mOriginalSize.height - 1);
  } else {
    // If we have a vertical offset, commit rows to shift us past it.
    SkipToRow(mFrameRect.Y());
  }
}

void
Downscaler::ClearRestOfRow(uint32_t aStartingAtCol)
{
  MOZ_ASSERT(int64_t(aStartingAtCol) <= int64_t(mOriginalSize.width));
  uint32_t bytesToClear = (mOriginalSize.width - aStartingAtCol)
                        * sizeof(uint32_t);
  memset(mRowBuffer.get() + (aStartingAtCol * sizeof(uint32_t)),
         0, bytesToClear);
}

void
Downscaler::CommitRow()
{
  MOZ_ASSERT(mOutputBuffer, "Should have a current frame");
  MOZ_ASSERT(mCurrentInLine < mOriginalSize.height, "Past end of input");

  if (mCurrentOutLine < mTargetSize.height) {
    int32_t filterOffset = 0;
    int32_t filterLength = 0;
    mYFilter.GetFilterOffsetAndLength(mCurrentOutLine,
                                      &filterOffset, &filterLength);

    int32_t inLineToRead = filterOffset + mLinesInBuffer;
    MOZ_ASSERT(mCurrentInLine <= inLineToRead, "Reading past end of input");
    if (mCurrentInLine == inLineToRead) {
      mXFilter.ConvolveHorizontally(mRowBuffer.get(), mWindow[mLinesInBuffer++], mHasAlpha);
    }

    MOZ_ASSERT(mCurrentOutLine < mTargetSize.height,
               "Writing past end of output");

    while (mLinesInBuffer == filterLength) {
      DownscaleInputLine();

      if (mCurrentOutLine == mTargetSize.height) {
        break;  // We're done.
      }

      mYFilter.GetFilterOffsetAndLength(mCurrentOutLine,
                                        &filterOffset, &filterLength);
    }
  }

  mCurrentInLine += 1;

  // If we're at the end of the part of the original image that has data, commit
  // rows to shift us to the end.
  if (mCurrentInLine == (mFrameRect.Y() + mFrameRect.Height())) {
    SkipToRow(mOriginalSize.height - 1);
  }
}

bool
Downscaler::HasInvalidation() const
{
  return mCurrentOutLine > mPrevInvalidatedLine;
}

DownscalerInvalidRect
Downscaler::TakeInvalidRect()
{
  if (MOZ_UNLIKELY(!HasInvalidation())) {
    return DownscalerInvalidRect();
  }

  DownscalerInvalidRect invalidRect;

  // Compute the target size invalid rect.
  if (mFlipVertically) {
    // We need to flip it. This will implicitly flip the original size invalid
    // rect, since we compute it by scaling this rect.
    invalidRect.mTargetSizeRect =
      IntRect(0, mTargetSize.height - mCurrentOutLine,
              mTargetSize.width, mCurrentOutLine - mPrevInvalidatedLine);
  } else {
    invalidRect.mTargetSizeRect =
      IntRect(0, mPrevInvalidatedLine,
              mTargetSize.width, mCurrentOutLine - mPrevInvalidatedLine);
  }

  mPrevInvalidatedLine = mCurrentOutLine;

  // Compute the original size invalid rect.
  invalidRect.mOriginalSizeRect = invalidRect.mTargetSizeRect;
  invalidRect.mOriginalSizeRect.ScaleRoundOut(mScale.width, mScale.height);

  return invalidRect;
}

void
Downscaler::DownscaleInputLine()
{
  MOZ_ASSERT(mOutputBuffer);
  MOZ_ASSERT(mCurrentOutLine < mTargetSize.height,
             "Writing past end of output");

  int32_t filterOffset = 0;
  int32_t filterLength = 0;
  mYFilter.GetFilterOffsetAndLength(mCurrentOutLine,
                                    &filterOffset, &filterLength);

  int32_t currentOutLine = mFlipVertically
                         ? mTargetSize.height - (mCurrentOutLine + 1)
                         : mCurrentOutLine;
  MOZ_ASSERT(currentOutLine >= 0);

  uint8_t* outputLine =
    &mOutputBuffer[currentOutLine * mTargetSize.width * sizeof(uint32_t)];
  mYFilter.ConvolveVertically(mWindow.get(), outputLine, mCurrentOutLine, mXFilter.NumValues(), mHasAlpha);

  mCurrentOutLine += 1;

  if (mCurrentOutLine == mTargetSize.height) {
    // We're done.
    return;
  }

  int32_t newFilterOffset = 0;
  int32_t newFilterLength = 0;
  mYFilter.GetFilterOffsetAndLength(mCurrentOutLine,
                                    &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.
  mLinesInBuffer -= diff;
  mLinesInBuffer = max(mLinesInBuffer, 0);
  for (int32_t i = 0; i < mLinesInBuffer; ++i) {
    swap(mWindow[i], mWindow[filterLength - mLinesInBuffer + i]);
  }
}



} // namespace image
} // namespace mozilla