tor-browser

ImageScaling.cpp (8022B)

---

/* -*- 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/. */

#include "ImageScaling.h"
#include "2D.h"
#include "DataSurfaceHelpers.h"

#include <math.h>
#include <algorithm>

namespace mozilla {
namespace gfx {

inline uint32_t Avg2x2(uint32_t a, uint32_t b, uint32_t c, uint32_t d) {
 // Prepare half-adder work
 uint32_t sum = a ^ b ^ c;
 uint32_t carry = (a & b) | (a & c) | (b & c);

 // Before shifting, mask lower order bits of each byte to avoid underflow.
 uint32_t mask = 0xfefefefe;

 // Add d to sum and divide by 2.
 sum = (((sum ^ d) & mask) >> 1) + (sum & d);

 // Sum is now shifted into place relative to carry, add them together.
 return (((sum ^ carry) & mask) >> 1) + (sum & carry);
}

inline uint32_t Avg2(uint32_t a, uint32_t b) {
 // Prepare half-adder work
 uint32_t sum = a ^ b;
 uint32_t carry = (a & b);

 // Before shifting, mask lower order bits of each byte to avoid underflow.
 uint32_t mask = 0xfefefefe;

 // Add d to sum and divide by 2.
 return ((sum & mask) >> 1) + carry;
}

void ImageHalfScaler::ScaleForSize(const IntSize& aSize) {
 uint32_t horizontalDownscales = 0;
 uint32_t verticalDownscales = 0;

 IntSize scaleSize = mOrigSize;
 while ((scaleSize.height / 2) > aSize.height) {
   verticalDownscales++;
   scaleSize.height /= 2;
 }

 while ((scaleSize.width / 2) > aSize.width) {
   horizontalDownscales++;
   scaleSize.width /= 2;
 }

 if (scaleSize == mOrigSize) {
   return;
 }

 delete[] mDataStorage;

 IntSize internalSurfSize;
 internalSurfSize.width = std::max(scaleSize.width, mOrigSize.width / 2);
 internalSurfSize.height = std::max(scaleSize.height, mOrigSize.height / 2);

 size_t bufLen = 0;
 mStride = GetAlignedStride<16>(internalSurfSize.width, 4);
 if (mStride > 0) {
   // Allocate 15 bytes extra to make sure we can get 16 byte alignment. We
   // should add tools for this, see bug 751696.
   bufLen =
       BufferSizeFromStrideAndHeight(mStride, internalSurfSize.height, 15);
 }

 if (bufLen == 0) {
   mSize.SizeTo(0, 0);
   mDataStorage = nullptr;
   return;
 }
 mDataStorage = new uint8_t[bufLen];

 if (uintptr_t(mDataStorage) % 16) {
   // Our storage does not start at a 16-byte boundary. Make sure mData does!
   mData = (uint8_t*)(uintptr_t(mDataStorage) +
                      (16 - (uintptr_t(mDataStorage) % 16)));
 } else {
   mData = mDataStorage;
 }

 mSize = scaleSize;

 /* The surface we sample from might not be even sized, if it's not we will
  * ignore the last row/column. This means we lose some data but it keeps the
  * code very simple. There's also no perfect answer that provides a better
  * solution.
  */
 IntSize currentSampledSize = mOrigSize;
 uint32_t currentSampledStride = mOrigStride;
 uint8_t* currentSampledData = mOrigData;

 while (verticalDownscales && horizontalDownscales) {
   if (currentSampledSize.width % 2) {
     currentSampledSize.width -= 1;
   }
   if (currentSampledSize.height % 2) {
     currentSampledSize.height -= 1;
   }

   HalfImage2D(currentSampledData, currentSampledStride, currentSampledSize,
               mData, mStride);

   verticalDownscales--;
   horizontalDownscales--;
   currentSampledSize.width /= 2;
   currentSampledSize.height /= 2;
   currentSampledData = mData;
   currentSampledStride = mStride;
 }

 while (verticalDownscales) {
   if (currentSampledSize.height % 2) {
     currentSampledSize.height -= 1;
   }

   HalfImageVertical(currentSampledData, currentSampledStride,
                     currentSampledSize, mData, mStride);

   verticalDownscales--;
   currentSampledSize.height /= 2;
   currentSampledData = mData;
   currentSampledStride = mStride;
 }

 while (horizontalDownscales) {
   if (currentSampledSize.width % 2) {
     currentSampledSize.width -= 1;
   }

   HalfImageHorizontal(currentSampledData, currentSampledStride,
                       currentSampledSize, mData, mStride);

   horizontalDownscales--;
   currentSampledSize.width /= 2;
   currentSampledData = mData;
   currentSampledStride = mStride;
 }
}

void ImageHalfScaler::HalfImage2D(uint8_t* aSource, int32_t aSourceStride,
                                 const IntSize& aSourceSize, uint8_t* aDest,
                                 uint32_t aDestStride) {
#ifdef USE_SSE2
 if (Factory::HasSSE2()) {
   HalfImage2D_SSE2(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
 } else
#endif
 {
   HalfImage2D_C(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
 }
}

void ImageHalfScaler::HalfImageVertical(uint8_t* aSource, int32_t aSourceStride,
                                       const IntSize& aSourceSize,
                                       uint8_t* aDest, uint32_t aDestStride) {
#ifdef USE_SSE2
 if (Factory::HasSSE2()) {
   HalfImageVertical_SSE2(aSource, aSourceStride, aSourceSize, aDest,
                          aDestStride);
 } else
#endif
 {
   HalfImageVertical_C(aSource, aSourceStride, aSourceSize, aDest,
                       aDestStride);
 }
}

void ImageHalfScaler::HalfImageHorizontal(uint8_t* aSource,
                                         int32_t aSourceStride,
                                         const IntSize& aSourceSize,
                                         uint8_t* aDest,
                                         uint32_t aDestStride) {
#ifdef USE_SSE2
 if (Factory::HasSSE2()) {
   HalfImageHorizontal_SSE2(aSource, aSourceStride, aSourceSize, aDest,
                            aDestStride);
 } else
#endif
 {
   HalfImageHorizontal_C(aSource, aSourceStride, aSourceSize, aDest,
                         aDestStride);
 }
}

void ImageHalfScaler::HalfImage2D_C(uint8_t* aSource, int32_t aSourceStride,
                                   const IntSize& aSourceSize, uint8_t* aDest,
                                   uint32_t aDestStride) {
 for (int y = 0; y < aSourceSize.height; y += 2) {
   uint32_t* storage = (uint32_t*)(aDest + (y / 2) * aDestStride);
   for (int x = 0; x < aSourceSize.width; x += 2) {
     uint8_t* upperRow = aSource + (y * aSourceStride + x * 4);
     uint8_t* lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);

     *storage++ = Avg2x2(*(uint32_t*)upperRow, *((uint32_t*)upperRow + 1),
                         *(uint32_t*)lowerRow, *((uint32_t*)lowerRow + 1));
   }
 }
}

void ImageHalfScaler::HalfImageVertical_C(uint8_t* aSource,
                                         int32_t aSourceStride,
                                         const IntSize& aSourceSize,
                                         uint8_t* aDest,
                                         uint32_t aDestStride) {
 for (int y = 0; y < aSourceSize.height; y += 2) {
   uint32_t* storage = (uint32_t*)(aDest + (y / 2) * aDestStride);
   for (int x = 0; x < aSourceSize.width; x++) {
     uint32_t* upperRow = (uint32_t*)(aSource + (y * aSourceStride + x * 4));
     uint32_t* lowerRow =
         (uint32_t*)(aSource + ((y + 1) * aSourceStride + x * 4));

     *storage++ = Avg2(*upperRow, *lowerRow);
   }
 }
}

void ImageHalfScaler::HalfImageHorizontal_C(uint8_t* aSource,
                                           int32_t aSourceStride,
                                           const IntSize& aSourceSize,
                                           uint8_t* aDest,
                                           uint32_t aDestStride) {
 for (int y = 0; y < aSourceSize.height; y++) {
   uint32_t* storage = (uint32_t*)(aDest + y * aDestStride);
   for (int x = 0; x < aSourceSize.width; x += 2) {
     uint32_t* pixels = (uint32_t*)(aSource + (y * aSourceStride + x * 4));

     *storage++ = Avg2(*pixels, *(pixels + 1));
   }
 }
}

}  // namespace gfx
}  // namespace mozilla