/* -*- 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>

using namespace std;

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 = max(scaleSize.width, mOrigSize.width / 2);

  internalSurfSize.height = 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