image/Downscaler.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "Downscaler.h"
   8
   9 #include <algorithm>
  10 #include <ctime>
  11
  12 #include "mozilla/gfx/2D.h"
  13
  14 using std::max;
  15 using std::swap;
  16
  17 namespace mozilla {
  18
  19 using gfx::IntRect;
  20
  21 namespace image {
  22
  23 Downscaler::Downscaler(const nsIntSize& aTargetSize)
  24     : mTargetSize(aTargetSize),
  25       mOutputBuffer(nullptr),
  26       mWindowCapacity(0),
  27       mLinesInBuffer(0),
  28       mPrevInvalidatedLine(0),
  29       mCurrentOutLine(0),
  30       mCurrentInLine(0),
  31       mHasAlpha(true),
  32       mFlipVertically(false) {
  33   MOZ_ASSERT(mTargetSize.width > 0 && mTargetSize.height > 0,
  34              "Invalid target size");
  35 }
  36
  37 Downscaler::~Downscaler() { ReleaseWindow(); }
  38
  39 void Downscaler::ReleaseWindow() {
  40   if (!mWindow) {
  41     return;
  42   }
  43
  44   for (int32_t i = 0; i < mWindowCapacity; ++i) {
  45     delete[] mWindow[i];
  46   }
  47
  48   mWindow = nullptr;
  49   mWindowCapacity = 0;
  50 }
  51
  52 nsresult Downscaler::BeginFrame(const nsIntSize& aOriginalSize,
  53                                 const Maybe<nsIntRect>& aFrameRect,
  54                                 uint8_t* aOutputBuffer, bool aHasAlpha,
  55                                 bool aFlipVertically /* = false */) {
  56   MOZ_ASSERT(aOutputBuffer);
  57   MOZ_ASSERT(mTargetSize != aOriginalSize,
  58              "Created a downscaler, but not downscaling?");
  59   MOZ_ASSERT(mTargetSize.width <= aOriginalSize.width,
  60              "Created a downscaler, but width is larger");
  61   MOZ_ASSERT(mTargetSize.height <= aOriginalSize.height,
  62              "Created a downscaler, but height is larger");
  63   MOZ_ASSERT(aOriginalSize.width > 0 && aOriginalSize.height > 0,
  64              "Invalid original size");
  65
  66   // Only downscale from reasonable sizes to avoid using too much memory/cpu
  67   // downscaling and decoding. 1 << 20 == 1,048,576 seems a reasonable limit.
  68   if (aOriginalSize.width > (1 << 20) || aOriginalSize.height > (1 << 20)) {
  69     NS_WARNING("Trying to downscale image frame that is too large");
  70     return NS_ERROR_INVALID_ARG;
  71   }
  72
  73   mFrameRect = aFrameRect.valueOr(nsIntRect(nsIntPoint(), aOriginalSize));
  74   MOZ_ASSERT(mFrameRect.X() >= 0 && mFrameRect.Y() >= 0 &&
  75                  mFrameRect.Width() >= 0 && mFrameRect.Height() >= 0,
  76              "Frame rect must have non-negative components");
  77   MOZ_ASSERT(nsIntRect(0, 0, aOriginalSize.width, aOriginalSize.height)
  78                  .Contains(mFrameRect),
  79              "Frame rect must fit inside image");
  80   MOZ_ASSERT_IF(!nsIntRect(0, 0, aOriginalSize.width, aOriginalSize.height)
  81                      .IsEqualEdges(mFrameRect),
  82                 aHasAlpha);
  83
  84   mOriginalSize = aOriginalSize;
  85   mScale = gfxSize(double(mOriginalSize.width) / mTargetSize.width,
  86                    double(mOriginalSize.height) / mTargetSize.height);
  87   mOutputBuffer = aOutputBuffer;
  88   mHasAlpha = aHasAlpha;
  89   mFlipVertically = aFlipVertically;
  90
  91   ReleaseWindow();
  92
  93   auto resizeMethod = gfx::ConvolutionFilter::ResizeMethod::LANCZOS3;
  94   if (!mXFilter.ComputeResizeFilter(resizeMethod, mOriginalSize.width,
  95                                     mTargetSize.width) ||
  96       !mYFilter.ComputeResizeFilter(resizeMethod, mOriginalSize.height,
  97                                     mTargetSize.height)) {
  98     NS_WARNING("Failed to compute filters for image downscaling");
  99     return NS_ERROR_OUT_OF_MEMORY;
 100   }
 101
 102   // Allocate the buffer, which contains scanlines of the original image.
 103   // pad to handle overreads by the simd code
 104   size_t bufferLen = gfx::ConvolutionFilter::PadBytesForSIMD(
 105       mOriginalSize.width * sizeof(uint32_t));
 106   mRowBuffer.reset(new (fallible) uint8_t[bufferLen]);
 107   if (MOZ_UNLIKELY(!mRowBuffer)) {
 108     return NS_ERROR_OUT_OF_MEMORY;
 109   }
 110
 111   // Zero buffer to keep valgrind happy.
 112   memset(mRowBuffer.get(), 0, bufferLen);
 113
 114   // Allocate the window, which contains horizontally downscaled scanlines. (We
 115   // can store scanlines which are already downscale because our downscaling
 116   // filter is separable.)
 117   mWindowCapacity = mYFilter.MaxFilter();
 118   mWindow.reset(new (fallible) uint8_t*[mWindowCapacity]);
 119   if (MOZ_UNLIKELY(!mWindow)) {
 120     return NS_ERROR_OUT_OF_MEMORY;
 121   }
 122
 123   bool anyAllocationFailed = false;
 124   // pad to handle overreads by the simd code
 125   const size_t rowSize = gfx::ConvolutionFilter::PadBytesForSIMD(
 126       mTargetSize.width * sizeof(uint32_t));
 127   for (int32_t i = 0; i < mWindowCapacity; ++i) {
 128     mWindow[i] = new (fallible) uint8_t[rowSize];
 129     anyAllocationFailed = anyAllocationFailed || mWindow[i] == nullptr;
 130   }
 131
 132   if (MOZ_UNLIKELY(anyAllocationFailed)) {
 133     // We intentionally iterate through the entire array even if an allocation
 134     // fails, to ensure that all the pointers in it are either valid or nullptr.
 135     // That in turn ensures that ReleaseWindow() can clean up correctly.
 136     return NS_ERROR_OUT_OF_MEMORY;
 137   }
 138
 139   ResetForNextProgressivePass();
 140
 141   return NS_OK;
 142 }
 143
 144 void Downscaler::SkipToRow(int32_t aRow) {
 145   if (mCurrentInLine < aRow) {
 146     ClearRow();
 147     do {
 148       CommitRow();
 149     } while (mCurrentInLine < aRow);
 150   }
 151 }
 152
 153 void Downscaler::ResetForNextProgressivePass() {
 154   mPrevInvalidatedLine = 0;
 155   mCurrentOutLine = 0;
 156   mCurrentInLine = 0;
 157   mLinesInBuffer = 0;
 158
 159   if (mFrameRect.IsEmpty()) {
 160     // Our frame rect is zero size; commit rows until the end of the image.
 161     SkipToRow(mOriginalSize.height - 1);
 162   } else {
 163     // If we have a vertical offset, commit rows to shift us past it.
 164     SkipToRow(mFrameRect.Y());
 165   }
 166 }
 167
 168 void Downscaler::ClearRestOfRow(uint32_t aStartingAtCol) {
 169   MOZ_ASSERT(int64_t(aStartingAtCol) <= int64_t(mOriginalSize.width));
 170   uint32_t bytesToClear =
 171       (mOriginalSize.width - aStartingAtCol) * sizeof(uint32_t);
 172   memset(mRowBuffer.get() + (aStartingAtCol * sizeof(uint32_t)), 0,
 173          bytesToClear);
 174 }
 175
 176 void Downscaler::CommitRow() {
 177   MOZ_ASSERT(mOutputBuffer, "Should have a current frame");
 178   MOZ_ASSERT(mCurrentInLine < mOriginalSize.height, "Past end of input");
 179
 180   if (mCurrentOutLine < mTargetSize.height) {
 181     int32_t filterOffset = 0;
 182     int32_t filterLength = 0;
 183     mYFilter.GetFilterOffsetAndLength(mCurrentOutLine, &filterOffset,
 184                                       &filterLength);
 185
 186     int32_t inLineToRead = filterOffset + mLinesInBuffer;
 187     MOZ_ASSERT(mCurrentInLine <= inLineToRead, "Reading past end of input");
 188     if (mCurrentInLine == inLineToRead) {
 189       MOZ_RELEASE_ASSERT(mLinesInBuffer < mWindowCapacity,
 190                          "Need more rows than capacity!");
 191       mXFilter.ConvolveHorizontally(mRowBuffer.get(), mWindow[mLinesInBuffer++],
 192                                     mHasAlpha);
 193     }
 194
 195     MOZ_ASSERT(mCurrentOutLine < mTargetSize.height,
 196                "Writing past end of output");
 197
 198     while (mLinesInBuffer >= filterLength) {
 199       DownscaleInputLine();
 200
 201       if (mCurrentOutLine == mTargetSize.height) {
 202         break;  // We're done.
 203       }
 204
 205       mYFilter.GetFilterOffsetAndLength(mCurrentOutLine, &filterOffset,
 206                                         &filterLength);
 207     }
 208   }
 209
 210   mCurrentInLine += 1;
 211
 212   // If we're at the end of the part of the original image that has data, commit
 213   // rows to shift us to the end.
 214   if (mCurrentInLine == (mFrameRect.Y() + mFrameRect.Height())) {
 215     SkipToRow(mOriginalSize.height - 1);
 216   }
 217 }
 218
 219 bool Downscaler::HasInvalidation() const {
 220   return mCurrentOutLine > mPrevInvalidatedLine;
 221 }
 222
 223 DownscalerInvalidRect Downscaler::TakeInvalidRect() {
 224   if (MOZ_UNLIKELY(!HasInvalidation())) {
 225     return DownscalerInvalidRect();
 226   }
 227
 228   DownscalerInvalidRect invalidRect;
 229
 230   // Compute the target size invalid rect.
 231   if (mFlipVertically) {
 232     // We need to flip it. This will implicitly flip the original size invalid
 233     // rect, since we compute it by scaling this rect.
 234     invalidRect.mTargetSizeRect =
 235         IntRect(0, mTargetSize.height - mCurrentOutLine, mTargetSize.width,
 236                 mCurrentOutLine - mPrevInvalidatedLine);
 237   } else {
 238     invalidRect.mTargetSizeRect =
 239         IntRect(0, mPrevInvalidatedLine, mTargetSize.width,
 240                 mCurrentOutLine - mPrevInvalidatedLine);
 241   }
 242
 243   mPrevInvalidatedLine = mCurrentOutLine;
 244
 245   // Compute the original size invalid rect.
 246   invalidRect.mOriginalSizeRect = invalidRect.mTargetSizeRect;
 247   invalidRect.mOriginalSizeRect.ScaleRoundOut(mScale.width, mScale.height);
 248
 249   return invalidRect;
 250 }
 251
 252 void Downscaler::DownscaleInputLine() {
 253   MOZ_ASSERT(mOutputBuffer);
 254   MOZ_ASSERT(mCurrentOutLine < mTargetSize.height,
 255              "Writing past end of output");
 256
 257   int32_t filterOffset = 0;
 258   int32_t filterLength = 0;
 259   mYFilter.GetFilterOffsetAndLength(mCurrentOutLine, &filterOffset,
 260                                     &filterLength);
 261
 262   int32_t currentOutLine = mFlipVertically
 263                                ? mTargetSize.height - (mCurrentOutLine + 1)
 264                                : mCurrentOutLine;
 265   MOZ_ASSERT(currentOutLine >= 0);
 266
 267   uint8_t* outputLine =
 268       &mOutputBuffer[currentOutLine * mTargetSize.width * sizeof(uint32_t)];
 269   mYFilter.ConvolveVertically(mWindow.get(), outputLine, mCurrentOutLine,
 270                               mXFilter.NumValues(), mHasAlpha);
 271
 272   mCurrentOutLine += 1;
 273
 274   if (mCurrentOutLine == mTargetSize.height) {
 275     // We're done.
 276     return;
 277   }
 278
 279   int32_t newFilterOffset = 0;
 280   int32_t newFilterLength = 0;
 281   mYFilter.GetFilterOffsetAndLength(mCurrentOutLine, &newFilterOffset,
 282                                     &newFilterLength);
 283
 284   int diff = newFilterOffset - filterOffset;
 285   MOZ_ASSERT(diff >= 0, "Moving backwards in the filter?");
 286
 287   // Shift the buffer. We're just moving pointers here, so this is cheap.
 288   mLinesInBuffer -= diff;
 289   mLinesInBuffer = std::min(std::max(mLinesInBuffer, 0), mWindowCapacity);
 290
 291   // If we already have enough rows to satisfy the filter, there is no need
 292   // to swap as we won't be writing more before the next convolution.
 293   if (filterLength > mLinesInBuffer) {
 294     for (int32_t i = 0; i < mLinesInBuffer; ++i) {
 295       swap(mWindow[i], mWindow[filterLength - mLinesInBuffer + i]);
 296     }
 297   }
 298 }
 299
 300 }  // namespace image
 301 }  // namespace mozilla