image/DownscalingFilter.h
author Ryan VanderMeulen <ryanvm@gmail.com>
Wed, 17 Jan 2018 15:55:38 -0500
changeset 399709 ef04f3ad847540c876c130b7d140a960d922a024
parent 367794 31f3099d70826885f85a1d57e3efd77480a3267c
child 403098 4afd35f217c1bc90ecdd6b010d564852a59c5eca
permissions -rw-r--r--
Backed out 20 changesets (bug 1411654) for incorrect android:debuggable. r=nalexander, a=RyanVM Backed out changeset cfad693be918 (bug 1411654) Backed out changeset 55776829a744 (bug 1411654) Backed out changeset c5bf85d56fed (bug 1411654) Backed out changeset c270f97bb0da (bug 1411654) Backed out changeset fde9bf9c14c3 (bug 1411654) Backed out changeset 01836fd98c63 (bug 1411654) Backed out changeset 730a70767743 (bug 1411654) Backed out changeset 690e265c684c (bug 1411654) Backed out changeset f918500d9cf5 (bug 1411654) Backed out changeset cec2b8828cc8 (bug 1411654) Backed out changeset 76085ddd5ac7 (bug 1411654) Backed out changeset 2b37201606f5 (bug 1411654) Backed out changeset d0d513d1c379 (bug 1411654) Backed out changeset e7b0cc801cf1 (bug 1411654) Backed out changeset 901b304603d9 (bug 1411654) Backed out changeset 373c9a71d945 (bug 1411654) Backed out changeset 3dc3beab95f8 (bug 1411654) Backed out changeset 22a861db1573 (bug 1411654) Backed out changeset 0850b319efd4 (bug 1411654) Backed out changeset d276d3deba05 (bug 1411654)

/* -*- 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/. */

/**
 * 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 "gfxPrefs.h"

#ifdef MOZ_ENABLE_SKIA
#include "mozilla/gfx/ConvolutionFilter.h"
#endif

#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.)
};

#ifndef MOZ_ENABLE_SKIA

/**
 * DownscalingFilter requires Skia. This is a fallback implementation for
 * non-Skia builds that fails when Configure() is called (which will prevent
 * SurfacePipeFactory from returning an instance of it) and crashes if a caller
 * manually constructs an instance and attempts to actually use it. Callers
 * should avoid this by ensuring that they do not request downscaling in
 * non-Skia builds.
 */
template <typename Next>
class DownscalingFilter final : public SurfaceFilter
{
public:
  Maybe<SurfaceInvalidRect> TakeInvalidRect() override { return Nothing(); }

  template <typename... Rest>
  nsresult Configure(const DownscalingConfig& aConfig, Rest... aRest)
  {
    return NS_ERROR_FAILURE;
  }

protected:
  uint8_t* DoResetToFirstRow() override { MOZ_CRASH(); return nullptr; }
  uint8_t* DoAdvanceRow() override { MOZ_CRASH(); return nullptr; }
};

#else

/**
 * 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)
  {
    MOZ_ASSERT(gfxPrefs::ImageDownscaleDuringDecodeEnabled(),
               "Downscaling even though downscale-during-decode is disabled?");
  }

  ~DownscalingFilter()
  {
    ReleaseWindow();
  }

  template <typename... Rest>
  nsresult Configure(const DownscalingConfig& aConfig, Rest... aRest)
  {
    nsresult rv = mNext.Configure(aRest...);
    if (NS_FAILED(rv)) {
      return rv;
    }

    if (mNext.IsValidPalettedPipe()) {
      NS_WARNING("Created a downscaler for a paletted surface?");
      return NS_ERROR_INVALID_ARG;
    }
    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 = gfxSize(double(mInputSize.width) / outputSize.width,
                     double(mInputSize.height) / outputSize.height);
    mHasAlpha = aConfig.mFormat == gfx::SurfaceFormat::B8G8R8A8;

    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.width, mScale.height);
    }

    return invalidRect;
  }

protected:
  uint8_t* DoResetToFirstRow() override
  {
    mNext.ResetToFirstRow();

    mInputRow = 0;
    mOutputRow = 0;
    mRowsInWindow = 0;

    return GetRowPointer();
  }

  uint8_t* DoAdvanceRow() 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) {
      mXFilter.ConvolveHorizontally(mRowBuffer.get(), 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;
  }

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::max(mRowsInWindow, 0);
    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.
  gfxSize 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.
};

#endif

} // namespace image
} // namespace mozilla

#endif // mozilla_image_DownscalingFilter_h