Merge "Add SetInterval, Pause, and Resume APIs in Timer" into devel/master

[platform/core/uifw/dali-adaptor.git] / dali / internal / imaging / common / image-operations.cpp

/*
 * Copyright (c) 2018 Samsung Electronics Co., Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include <dali/internal/imaging/common/image-operations.h>

// EXTERNAL INCLUDES
#include <cstring>
#include <stddef.h>
#include <cmath>
#include <limits>
#include <dali/integration-api/debug.h>
#include <dali/public-api/common/dali-vector.h>
#include <dali/public-api/math/vector2.h>
#include <third-party/resampler/resampler.h>
#include <dali/devel-api/adaptor-framework/image-loading.h>

// INTERNAL INCLUDES

namespace Dali
{
namespace Internal
{
namespace Platform
{

namespace
{

// The BORDER_FILL_VALUE is a single byte value that is used for horizontal and vertical borders.
// A value of 0x00 gives us transparency for pixel buffers with an alpha channel, or black otherwise.
// We can optionally use a Vector4 color here, but at reduced fill speed.
const uint8_t BORDER_FILL_VALUE( 0x00 );
// A maximum size limit for newly created bitmaps. ( 1u << 16 ) - 1 is chosen as we are using 16bit words for dimensions.
const unsigned int MAXIMUM_TARGET_BITMAP_SIZE( ( 1u << 16 ) - 1 );

// Constants used by the ImageResampler.
const float DEFAULT_SOURCE_GAMMA = 1.75f;   ///< Default source gamma value used in the Resampler() function. Partial gamma correction looks better on mips. Set to 1.0 to disable gamma correction.
const float FILTER_SCALE = 1.f;             ///< Default filter scale value used in the Resampler() function. Filter scale - values < 1.0 cause aliasing, but create sharper looking mips.

const float RAD_135 = Math::PI_2 + Math::PI_4; ///< 135 degrees in radians;
const float RAD_225 = RAD_135    + Math::PI_2; ///< 225 degrees in radians;
const float RAD_270 = 3.f * Math::PI_2;        ///< 270 degrees in radians;
const float RAD_315 = RAD_225    + Math::PI_2; ///< 315 degrees in radians;

using Integration::Bitmap;
using Integration::BitmapPtr;
typedef unsigned char PixelBuffer;

/**
 * @brief 4 byte pixel structure.
 */
struct Pixel4Bytes
{
  uint8_t r;
  uint8_t g;
  uint8_t b;
  uint8_t a;
} __attribute__((packed, aligned(4))); //< Tell the compiler it is okay to use a single 32 bit load.

/**
 * @brief RGB888 pixel structure.
 */
struct Pixel3Bytes
{
  uint8_t r;
  uint8_t g;
  uint8_t b;
} __attribute__((packed, aligned(1)));

/**
 * @brief RGB565 pixel typedefed from a short.
 *
 * Access fields by manual shifting and masking.
 */
typedef uint16_t PixelRGB565;

/**
 * @brief a Pixel composed of two independent byte components.
 */
struct Pixel2Bytes
{
  uint8_t l;
  uint8_t a;
} __attribute__((packed, aligned(2))); //< Tell the compiler it is okay to use a single 16 bit load.


#if defined(DEBUG_ENABLED)
/**
 * Disable logging of image operations or make it verbose from the commandline
 * as follows (e.g., for dali demo app):
 * <code>
 * LOG_IMAGE_OPERATIONS=0 dali-demo #< off
 * LOG_IMAGE_OPERATIONS=3 dali-demo #< on, verbose
 * </code>
 */
Debug::Filter* gImageOpsLogFilter = Debug::Filter::New( Debug::NoLogging, false, "LOG_IMAGE_OPERATIONS" );
#endif

/** @return The greatest even number less than or equal to the argument. */
inline unsigned int EvenDown( const unsigned int a )
{
  const unsigned int evened = a & ~1u;
  return evened;
}

/**
 * @brief Log bad parameters.
 */
void ValidateScalingParameters( const unsigned int inputWidth,
                                const unsigned int inputHeight,
                                const unsigned int desiredWidth,
                                const unsigned int desiredHeight )
{
  if( desiredWidth > inputWidth || desiredHeight > inputHeight )
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Upscaling not supported (%u, %u -> %u, %u).\n", inputWidth, inputHeight, desiredWidth, desiredHeight );
  }

  if( desiredWidth == 0u || desiredHeight == 0u )
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Downscaling to a zero-area target is pointless.\n" );
  }

  if( inputWidth == 0u || inputHeight == 0u )
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Zero area images cannot be scaled\n" );
  }
}

/**
 * @brief Do debug assertions common to all scanline halving functions.
 * @note Inline and in anon namespace so should boil away in release builds.
 */
inline void DebugAssertScanlineParameters( const uint8_t * const pixels, const unsigned int width )
{
  DALI_ASSERT_DEBUG( pixels && "Null pointer." );
  DALI_ASSERT_DEBUG( width > 1u && "Can't average fewer than two pixels." );
  DALI_ASSERT_DEBUG( width < 131072u && "Unusually wide image: are you sure you meant to pass that value in?" );
}

/**
 * @brief Assertions on params to functions averaging pairs of scanlines.
 * @note Inline as intended to boil away in release.
 */
inline void DebugAssertDualScanlineParameters( const uint8_t * const scanline1,
                                               const uint8_t * const scanline2,
                                               uint8_t* const outputScanline,
                                               const size_t widthInComponents )
{
  DALI_ASSERT_DEBUG( scanline1 && "Null pointer." );
  DALI_ASSERT_DEBUG( scanline2 && "Null pointer." );
  DALI_ASSERT_DEBUG( outputScanline && "Null pointer." );
  DALI_ASSERT_DEBUG( ((scanline1 >= scanline2 + widthInComponents) || (scanline2 >= scanline1 + widthInComponents )) && "Scanlines alias." );
  DALI_ASSERT_DEBUG( ((outputScanline >= (scanline2 + widthInComponents)) || (scanline2 >= (scanline1 + widthInComponents))) && "Scanline 2 aliases output." );
}

/**
 * @brief Converts a scaling mode to the definition of which dimensions matter when box filtering as a part of that mode.
 */
BoxDimensionTest DimensionTestForScalingMode( FittingMode::Type fittingMode )
{
  BoxDimensionTest dimensionTest;
  dimensionTest = BoxDimensionTestEither;

  switch( fittingMode )
  {
    // Shrink to fit attempts to make one or zero dimensions smaller than the
    // desired dimensions and one or two dimensions exactly the same as the desired
    // ones, so as long as one dimension is larger than the desired size, box
    // filtering can continue even if the second dimension is smaller than the
    // desired dimensions:
    case FittingMode::SHRINK_TO_FIT:
    {
      dimensionTest = BoxDimensionTestEither;
      break;
    }
    // Scale to fill mode keeps both dimensions at least as large as desired:
    case FittingMode::SCALE_TO_FILL:
    {
      dimensionTest = BoxDimensionTestBoth;
      break;
    }
    // Y dimension is irrelevant when downscaling in FIT_WIDTH mode:
    case FittingMode::FIT_WIDTH:
    {
      dimensionTest = BoxDimensionTestX;
      break;
    }
    // X Dimension is ignored by definition in FIT_HEIGHT mode:
    case FittingMode::FIT_HEIGHT:
    {
      dimensionTest = BoxDimensionTestY;
      break;
    }
  }

  return dimensionTest;
}

/**
 * @brief Work out the dimensions for a uniform scaling of the input to map it
 * into the target while effecting ShinkToFit scaling mode.
 */
ImageDimensions FitForShrinkToFit( ImageDimensions target, ImageDimensions source )
{
  // Scale the input by the least extreme of the two dimensions:
  const float widthScale  = target.GetX() / float(source.GetX());
  const float heightScale = target.GetY() / float(source.GetY());
  const float scale = widthScale < heightScale ? widthScale : heightScale;

  // Do no scaling at all if the result would increase area:
  if( scale >= 1.0f )
  {
    return source;
  }

  return ImageDimensions( source.GetX() * scale + 0.5f, source.GetY() * scale + 0.5f );
}

/**
 * @brief Work out the dimensions for a uniform scaling of the input to map it
 * into the target while effecting SCALE_TO_FILL scaling mode.
 * @note An image scaled into the output dimensions will need either top and
 * bottom or left and right to be cropped away unless the source was pre-cropped
 * to match the destination aspect ratio.
 */
ImageDimensions FitForScaleToFill( ImageDimensions target, ImageDimensions source )
{
  DALI_ASSERT_DEBUG( source.GetX() > 0 && source.GetY() > 0  && "Zero-area rectangles should not be passed-in" );
  // Scale the input by the least extreme of the two dimensions:
  const float widthScale  = target.GetX() / float(source.GetX());
  const float heightScale = target.GetY() / float(source.GetY());
  const float scale = widthScale > heightScale ? widthScale : heightScale;

  // Do no scaling at all if the result would increase area:
  if( scale >= 1.0f )
  {
    return source;
  }

  return ImageDimensions( source.GetX() * scale + 0.5f, source.GetY() * scale + 0.5f );
}

/**
 * @brief Work out the dimensions for a uniform scaling of the input to map it
 * into the target while effecting FIT_WIDTH scaling mode.
 */
ImageDimensions FitForFitWidth( ImageDimensions target, ImageDimensions source )
{
  DALI_ASSERT_DEBUG( source.GetX() > 0 && "Cant fit a zero-dimension rectangle." );
  const float scale  = target.GetX() / float(source.GetX());

  // Do no scaling at all if the result would increase area:
  if( scale >= 1.0f )
  {
   return source;
  }
  return ImageDimensions( source.GetX() * scale + 0.5f, source.GetY() * scale + 0.5f );
}

/**
 * @brief Work out the dimensions for a uniform scaling of the input to map it
 * into the target while effecting FIT_HEIGHT scaling mode.
 */
ImageDimensions FitForFitHeight( ImageDimensions target, ImageDimensions source )
{
  DALI_ASSERT_DEBUG( source.GetY() > 0 && "Cant fit a zero-dimension rectangle." );
  const float scale = target.GetY() / float(source.GetY());

  // Do no scaling at all if the result would increase area:
  if( scale >= 1.0f )
  {
    return source;
  }

  return ImageDimensions( source.GetX() * scale + 0.5f, source.GetY() * scale + 0.5f );
}

/**
 * @brief Generate the rectangle to use as the target of a pixel sampling pass
 * (e.g., nearest or linear).
 */
ImageDimensions FitToScalingMode( ImageDimensions requestedSize, ImageDimensions sourceSize, FittingMode::Type fittingMode )
{
  ImageDimensions fitDimensions;
  switch( fittingMode )
  {
    case FittingMode::SHRINK_TO_FIT:
    {
      fitDimensions = FitForShrinkToFit( requestedSize, sourceSize );
      break;
    }
    case FittingMode::SCALE_TO_FILL:
    {
      fitDimensions = FitForScaleToFill( requestedSize, sourceSize );
      break;
    }
    case FittingMode::FIT_WIDTH:
    {
      fitDimensions = FitForFitWidth( requestedSize, sourceSize );
      break;
    }
    case FittingMode::FIT_HEIGHT:
    {
      fitDimensions = FitForFitHeight( requestedSize, sourceSize );
      break;
    }
  }

  return fitDimensions;
}

/**
 * @brief Calculate the number of lines on the X and Y axis that need to be
 * either added or removed with repect to the specified fitting mode.
 * (e.g., nearest or linear).
 * @param[in]     sourceSize      The size of the source image
 * @param[in]     fittingMode     The fitting mode to use
 * @param[in/out] requestedSize   The target size that the image will be fitted to.
 *                                If the source image is smaller than the requested size, the source is not scaled up.
 *                                So we reduce the target size while keeping aspect by lowering resolution.
 * @param[out]    scanlinesToCrop The number of scanlines to remove from the image (can be negative to represent Y borders required)
 * @param[out]    columnsToCrop   The number of columns to remove from the image (can be negative to represent X borders required)
 */
void CalculateBordersFromFittingMode(  ImageDimensions sourceSize, FittingMode::Type fittingMode, ImageDimensions& requestedSize, int& scanlinesToCrop, int& columnsToCrop )
{
  const unsigned int sourceWidth( sourceSize.GetWidth() );
  const unsigned int sourceHeight( sourceSize.GetHeight() );
  const float targetAspect( static_cast< float >( requestedSize.GetWidth() ) / static_cast< float >( requestedSize.GetHeight() ) );
  int finalWidth = 0;
  int finalHeight = 0;

  switch( fittingMode )
  {
    case FittingMode::FIT_WIDTH:
    {
      finalWidth = sourceWidth;
      finalHeight = static_cast< float >( sourceWidth ) / targetAspect;

      columnsToCrop = 0;
      scanlinesToCrop = -( finalHeight - sourceHeight );
      break;
    }

    case FittingMode::FIT_HEIGHT:
    {
      finalWidth = static_cast< float >( sourceHeight ) * targetAspect;
      finalHeight = sourceHeight;

      columnsToCrop = -( finalWidth - sourceWidth );
      scanlinesToCrop = 0;
      break;
    }

    case FittingMode::SHRINK_TO_FIT:
    {
      const float sourceAspect( static_cast< float >( sourceWidth ) / static_cast< float >( sourceHeight ) );
      if( sourceAspect > targetAspect )
      {
        finalWidth = sourceWidth;
        finalHeight = static_cast< float >( sourceWidth ) / targetAspect;

        columnsToCrop = 0;
        scanlinesToCrop = -( finalHeight - sourceHeight );
      }
      else
      {
        finalWidth = static_cast< float >( sourceHeight ) * targetAspect;
        finalHeight = sourceHeight;

        columnsToCrop = -( finalWidth - sourceWidth );
        scanlinesToCrop = 0;
      }
      break;
    }

    case FittingMode::SCALE_TO_FILL:
    {
      const float sourceAspect( static_cast< float >( sourceWidth ) / static_cast< float >( sourceHeight ) );
      if( sourceAspect > targetAspect )
      {
        finalWidth = static_cast< float >( sourceHeight ) * targetAspect;
        finalHeight = sourceHeight;

        columnsToCrop = -( finalWidth - sourceWidth );
        scanlinesToCrop = 0;
      }
      else
      {
        finalWidth = sourceWidth;
        finalHeight = static_cast< float >( sourceWidth ) / targetAspect;

        columnsToCrop = 0;
        scanlinesToCrop = -( finalHeight - sourceHeight );
      }
      break;
    }
  }

  requestedSize.SetWidth( finalWidth );
  requestedSize.SetHeight( finalHeight );
}

/**
 * @brief Construct a pixel buffer object from a copy of the pixel array passed in.
 */
Dali::Devel::PixelBuffer MakePixelBuffer( const uint8_t * const pixels, Pixel::Format pixelFormat, unsigned int width, unsigned int height )
{
  DALI_ASSERT_DEBUG( pixels && "Null bitmap buffer to copy." );

  // Allocate a pixel buffer to hold the image passed in:
  auto newBitmap = Dali::Devel::PixelBuffer::New( width, height, pixelFormat );

  // Copy over the pixels from the downscaled image that was generated in-place in the pixel buffer of the input bitmap:
  memcpy( newBitmap.GetBuffer(), pixels, width * height * Pixel::GetBytesPerPixel( pixelFormat ) );
  return newBitmap;
}

/**
 * @brief Work out the desired width and height, accounting for zeros.
 *
 * @param[in] bitmapWidth Width of image before processing.
 * @param[in] bitmapHeight Height of image before processing.
 * @param[in] requestedWidth Width of area to scale image into. Can be zero.
 * @param[in] requestedHeight Height of area to scale image into. Can be zero.
 * @return Dimensions of area to scale image into after special rules are applied.
 */
ImageDimensions CalculateDesiredDimensions( unsigned int bitmapWidth, unsigned int bitmapHeight, unsigned int requestedWidth, unsigned int requestedHeight )
{
  unsigned int maxSize = Dali::GetMaxTextureSize();

  // If no dimensions have been requested, default to the source ones:
  if( requestedWidth == 0 && requestedHeight == 0 )
  {
    if( bitmapWidth <= maxSize && bitmapHeight <= maxSize )
    {
      return ImageDimensions( bitmapWidth, bitmapHeight );
    }
    else
    {
      // Calculate the size from the max texture size and the source image aspect ratio
      if( bitmapWidth > bitmapHeight )
      {
        return ImageDimensions( maxSize, bitmapHeight * maxSize / static_cast< float >( bitmapWidth ) + 0.5f );
      }
      else
      {
        return ImageDimensions( bitmapWidth * maxSize / static_cast< float >( bitmapHeight ) + 0.5f, maxSize );
      }
    }
  }

  // If both dimensions have values requested, use them both:
  if( requestedWidth != 0 && requestedHeight != 0 )
  {
    if( requestedWidth <= maxSize && requestedHeight <= maxSize )
    {
      return ImageDimensions( requestedWidth, requestedHeight );
    }
    else
    {
      // Calculate the size from the max texture size and the source image aspect ratio
      if( requestedWidth > requestedHeight )
      {
        return ImageDimensions( maxSize, requestedHeight * maxSize / static_cast< float >( requestedWidth ) + 0.5f );
      }
      else
      {
        return ImageDimensions( requestedWidth * maxSize / static_cast< float >( requestedHeight ) + 0.5f, maxSize );
      }
    }
  }

  // Only one of the dimensions has been requested. Calculate the other from
  // the requested one and the source image aspect ratio:
  if( requestedWidth != 0 )
  {
    requestedWidth = std::min( requestedWidth, maxSize );
    return ImageDimensions( requestedWidth, bitmapHeight / float(bitmapWidth) * requestedWidth + 0.5f );
  }

  requestedHeight = std::min( requestedHeight, maxSize );
  return ImageDimensions( bitmapWidth / float(bitmapHeight) * requestedHeight + 0.5f, requestedHeight );
}

/**
 * @brief Rotates the given buffer @p pixelsIn 90 degrees counter clockwise.
 *
 * @note It allocates memory for the returned @p pixelsOut buffer.
 * @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.
 *
 * @param[in] pixelsIn The input buffer.
 * @param[in] widthIn The width of the input buffer.
 * @param[in] heightIn The height of the input buffer.
 * @param[in] pixelSize The size of the pixel.
 * @param[out] pixelsOut The rotated output buffer.
 * @param[out] widthOut The width of the output buffer.
 * @param[out] heightOut The height of the output buffer.
 */
void Rotate90( const uint8_t* const pixelsIn,
               unsigned int widthIn,
               unsigned int heightIn,
               unsigned int pixelSize,
               uint8_t*& pixelsOut,
               unsigned int& widthOut,
               unsigned int& heightOut )
{
  // The new size of the image.
  widthOut = heightIn;
  heightOut = widthIn;

  // Allocate memory for the rotated buffer.
  pixelsOut = static_cast<uint8_t*>( malloc ( widthOut * heightOut * pixelSize ) );

  // Rotate the buffer.
  for( unsigned int y = 0u; y < heightIn; ++y )
  {
    const unsigned int srcLineIndex = y * widthIn;
    const unsigned int dstX = y;
    for( unsigned int x = 0u; x < widthIn; ++x )
    {
      const unsigned int dstY = heightOut - x - 1u;
      const unsigned int dstIndex = pixelSize * ( dstY * widthOut + dstX );
      const unsigned int srcIndex = pixelSize * ( srcLineIndex + x );

      for( unsigned int channel = 0u; channel < pixelSize; ++channel )
      {
        *( pixelsOut + dstIndex + channel ) = *( pixelsIn + srcIndex + channel );
      }
    }
  }
}

/**
 * @brief Rotates the given buffer @p pixelsIn 180 degrees counter clockwise.
 *
 * @note It allocates memory for the returned @p pixelsOut buffer.
 * @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.
 *
 * @param[in] pixelsIn The input buffer.
 * @param[in] widthIn The width of the input buffer.
 * @param[in] heightIn The height of the input buffer.
 * @param[in] pixelSize The size of the pixel.
 * @param[out] pixelsOut The rotated output buffer.
 */
void Rotate180( const uint8_t* const pixelsIn,
                unsigned int widthIn,
                unsigned int heightIn,
                unsigned int pixelSize,
                uint8_t*& pixelsOut )
{
  // Allocate memory for the rotated buffer.
  pixelsOut = static_cast<uint8_t*>( malloc ( widthIn * heightIn * pixelSize ) );

  // Rotate the buffer.
  for( unsigned int y = 0u; y < heightIn; ++y )
  {
    const unsigned int srcLineIndex = y * widthIn;
    const unsigned int dstY = heightIn - y - 1u;
    for( unsigned int x = 0u; x < widthIn; ++x )
    {
      const unsigned int dstX = widthIn - x - 1u;
      const unsigned int dstIndex = pixelSize * ( dstY * widthIn + dstX );
      const unsigned int srcIndex = pixelSize * ( srcLineIndex + x );

      for( unsigned int channel = 0u; channel < pixelSize; ++channel )
      {
        *( pixelsOut + dstIndex + channel ) = *( pixelsIn + srcIndex + channel );
      }
    }
  }
}

/**
 * @brief Rotates the given buffer @p pixelsIn 270 degrees counter clockwise.
 *
 * @note It allocates memory for the returned @p pixelsOut buffer.
 * @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.
 *
 * @param[in] pixelsIn The input buffer.
 * @param[in] widthIn The width of the input buffer.
 * @param[in] heightIn The height of the input buffer.
 * @param[in] pixelSize The size of the pixel.
 * @param[out] pixelsOut The rotated output buffer.
 * @param[out] widthOut The width of the output buffer.
 * @param[out] heightOut The height of the output buffer.
 */
void Rotate270( const uint8_t* const pixelsIn,
                unsigned int widthIn,
                unsigned int heightIn,
                unsigned int pixelSize,
                uint8_t*& pixelsOut,
                unsigned int& widthOut,
                unsigned int& heightOut )
{
  // The new size of the image.
  widthOut = heightIn;
  heightOut = widthIn;

  // Allocate memory for the rotated buffer.
  pixelsOut = static_cast<uint8_t*>( malloc ( widthOut * heightOut * pixelSize ) );

  // Rotate the buffer.
  for( unsigned int y = 0u; y < heightIn; ++y )
  {
    const unsigned int srcLineIndex = y * widthIn;
    const unsigned int dstX = widthOut - y - 1u;
    for( unsigned int x = 0u; x < widthIn; ++x )
    {
      const unsigned int dstY = x;
      const unsigned int dstIndex = pixelSize * ( dstY * widthOut + dstX );
      const unsigned int srcIndex = pixelSize * ( srcLineIndex + x );

      for( unsigned int channel = 0u; channel < pixelSize; ++channel )
      {
        *( pixelsOut + dstIndex + channel ) = *( pixelsIn + srcIndex + channel );
      }
    }
  }
}

/**
 * @brief Skews a row horizontally (with filtered weights)
 *
 * @note Limited to 45 degree skewing only.
 * @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.
 *
 * @param[in] srcBufferPtr Pointer to the input pixel buffer.
 * @param[in] srcWidth The width of the input pixel buffer.
 * @param[in] pixelSize The size of the pixel.
 * @param[in,out] dstPixelBuffer Pointer to the output pixel buffer.
 * @param[in] dstWidth The width of the output pixel buffer.
 * @param[in] row The row index.
 * @param[in] offset The skew offset.
 * @param[in] weight The relative weight of right pixel.
 */
void HorizontalSkew( const uint8_t* const srcBufferPtr,
                     int srcWidth,
                     unsigned int pixelSize,
                     uint8_t*& dstBufferPtr,
                     int dstWidth,
                     unsigned int row,
                     int offset,
                     float weight )
{
  if( offset > 0 )
  {
    // Fill gap left of skew with background.
    memset( dstBufferPtr + row * pixelSize * dstWidth, 0u, pixelSize * offset );
  }

  unsigned char oldLeft[4u] = { 0u, 0u, 0u, 0u };

  int i = 0;
  for( i = 0u; i < srcWidth; ++i )
  {
    // Loop through row pixels
    const unsigned int srcIndex = pixelSize * ( row * srcWidth + i );

    unsigned char src[4u] = { 0u, 0u, 0u, 0u };
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      src[channel] = *( srcBufferPtr + srcIndex + channel );
    }

    // Calculate weights
    unsigned char left[4u] = { 0u, 0u, 0u, 0u };
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      left[channel] = static_cast<unsigned char>( static_cast<float>( src[channel] ) * weight );

      // Update left over on source
      src[channel] -= ( left[channel] - oldLeft[channel] );
    }

    // Check boundaries
    if( ( i + offset >= 0 ) && ( i + offset < dstWidth ) )
    {
      const unsigned int dstIndex = pixelSize * ( row * dstWidth + i + offset );

      for( unsigned int channel = 0u; channel < pixelSize; ++channel )
      {
        *( dstBufferPtr + dstIndex + channel ) = src[channel];
      }
    }

    // Save leftover for next pixel in scan
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      oldLeft[channel] = left[channel];
    }
  }

  // Go to rightmost point of skew
  i += offset;
  if( i < dstWidth )
  {
    // If still in image bounds, put leftovers there
    const unsigned int dstIndex = pixelSize * ( row * dstWidth + i );

    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      *( dstBufferPtr + dstIndex + channel ) = oldLeft[channel];
    }

    // Clear to the right of the skewed line with background
    ++i;
    memset( dstBufferPtr + pixelSize * ( row * dstWidth + i ), 0u, pixelSize * ( dstWidth - i ) );
  }
}

/**
 * @brief Skews a column vertically (with filtered weights)
 *
 * @note Limited to 45 degree skewing only.
 * @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.
 *
 * @param[in] srcBufferPtr Pointer to the input pixel buffer.
 * @param[in] srcWidth The width of the input pixel buffer.
 * @param[in] srcHeight The height of the input pixel buffer.
 * @param[in] pixelSize The size of the pixel.
 * @param[in,out] dstPixelBuffer Pointer to the output pixel buffer.
 * @param[in] dstWidth The width of the output pixel buffer.
 * @param[in] dstHeight The height of the output pixel buffer.
 * @param[in] column The column index.
 * @param[in] offset The skew offset.
 * @param[in] weight The relative weight of uppeer pixel.
 */
void VerticalSkew( const uint8_t* const srcBufferPtr,
                   int srcWidth,
                   int srcHeight,
                   unsigned int pixelSize,
                   uint8_t*& dstBufferPtr,
                   int dstWidth,
                   int dstHeight,
                   unsigned int column,
                   int offset,
                   float weight )
{
  for( int i = 0; i < offset; ++i )
  {
    // Fill gap above skew with background
    const unsigned int dstIndex = pixelSize * ( i * dstWidth + column );

    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      *( dstBufferPtr + dstIndex + channel ) = 0u;
    }
  }

  unsigned char oldLeft[4u] = { 0u, 0u, 0u, 0u };

  int yPos = 0;
  int i = 0;
  for( i = 0; i < srcHeight; ++i )
  {
    // Loop through column pixels
    const unsigned int srcIndex = pixelSize * ( i * srcWidth + column );

    unsigned char src[4u] = { 0u, 0u, 0u, 0u };
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      src[channel] = *( srcBufferPtr + srcIndex + channel );
    }

    yPos = i + offset;

    // Calculate weights
    unsigned char left[4u] = { 0u, 0u, 0u, 0u };
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      left[channel] = static_cast<unsigned char>( static_cast<float>( src[channel] ) * weight );
      // Update left over on source
      src[channel] -= ( left[channel] - oldLeft[channel] );
    }

    // Check boundaries
    if( ( yPos >= 0 ) && ( yPos < dstHeight ) )
    {
      const unsigned int dstIndex = pixelSize * ( yPos * dstWidth + column );

      for( unsigned int channel = 0u; channel < pixelSize; ++channel )
      {
        *( dstBufferPtr + dstIndex + channel ) = src[channel];
      }
    }

    // Save leftover for next pixel in scan
    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      oldLeft[channel] = left[channel];
    }
  }

  // Go to bottom point of skew
  i = yPos;
  if( i < dstHeight )
  {
    // If still in image bounds, put leftovers there
    const unsigned int dstIndex = pixelSize * ( i * dstWidth + column );

    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      *( dstBufferPtr + dstIndex + channel ) = oldLeft[channel];
    }
  }

  while( ++i < dstHeight )
  {
    // Clear below skewed line with background
    const unsigned int dstIndex = pixelSize * ( i * dstWidth + column );

    for( unsigned int channel = 0u; channel < pixelSize; ++channel )
    {
      *( dstBufferPtr + dstIndex + channel ) = 0u;
    }
  }
}

} // namespace - unnamed

ImageDimensions CalculateDesiredDimensions( ImageDimensions rawDimensions, ImageDimensions requestedDimensions )
{
  return CalculateDesiredDimensions( rawDimensions.GetWidth(), rawDimensions.GetHeight(), requestedDimensions.GetWidth(), requestedDimensions.GetHeight() ) ;
}

/**
 * @brief Apply cropping and padding for specified fitting mode.
 *
 * Once the bitmap has been (optionally) downscaled to an appropriate size, this method performs alterations
 * based on the fitting mode.
 *
 * This will add vertical or horizontal borders if necessary.
 * Crop the source image data vertically or horizontally if necessary.
 * The aspect of the source image is preserved.
 * If the source image is smaller than the desired size, the algorithm will modify the the newly created
 *   bitmaps dimensions to only be as large as necessary, as a memory saving optimization. This will cause
 *   GPU scaling to be performed at render time giving the same result with less texture traversal.
 *
 * @param[in] bitmap            The source pixel buffer to perform modifications on.
 * @param[in] desiredDimensions The target dimensions to aim to fill based on the fitting mode.
 * @param[in] fittingMode       The fitting mode to use.
 *
 * @return                      A new bitmap with the padding and cropping required for fitting mode applied.
 *                              If no modification is needed or possible, the passed in bitmap is returned.
 */
Dali::Devel::PixelBuffer CropAndPadForFittingMode( Dali::Devel::PixelBuffer& bitmap, ImageDimensions desiredDimensions, FittingMode::Type fittingMode );

/**
 * @brief Adds horizontal or vertical borders to the source image.
 *
 * @param[in] targetPixels     The destination image pointer to draw the borders on.
 * @param[in] bytesPerPixel    The number of bytes per pixel of the target pixel buffer.
 * @param[in] targetDimensions The dimensions of the destination image.
 * @param[in] padDimensions    The columns and scanlines to pad with borders.
 */
void AddBorders( PixelBuffer *targetPixels, const unsigned int bytesPerPixel, const ImageDimensions targetDimensions, const ImageDimensions padDimensions );

Dali::Devel::PixelBuffer ApplyAttributesToBitmap( Dali::Devel::PixelBuffer bitmap, ImageDimensions dimensions, FittingMode::Type fittingMode, SamplingMode::Type samplingMode )
{
  if( bitmap )
  {
    // Calculate the desired box, accounting for a possible zero component:
    const ImageDimensions desiredDimensions  = CalculateDesiredDimensions( bitmap.GetWidth(), bitmap.GetHeight(), dimensions.GetWidth(), dimensions.GetHeight() );

    // If a different size than the raw one has been requested, resize the image
    // maximally using a repeated box filter without making it smaller than the
    // requested size in either dimension:
    bitmap = DownscaleBitmap( bitmap, desiredDimensions, fittingMode, samplingMode );

    // Cut the bitmap according to the desired width and height so that the
    // resulting bitmap has the same aspect ratio as the desired dimensions.
    // Add crop and add borders if necessary depending on fitting mode.
    if( bitmap )
    {
      bitmap = CropAndPadForFittingMode( bitmap, desiredDimensions, fittingMode );
    }
  }

  return bitmap;
}

Dali::Devel::PixelBuffer CropAndPadForFittingMode( Dali::Devel::PixelBuffer& bitmap, ImageDimensions desiredDimensions, FittingMode::Type fittingMode )
{
  const unsigned int inputWidth = bitmap.GetWidth();
  const unsigned int inputHeight = bitmap.GetHeight();

  if( desiredDimensions.GetWidth() < 1u || desiredDimensions.GetHeight() < 1u )
  {
    DALI_LOG_WARNING( "Image scaling aborted as desired dimensions too small (%u, %u).\n", desiredDimensions.GetWidth(), desiredDimensions.GetHeight() );
  }
  else if( inputWidth != desiredDimensions.GetWidth() || inputHeight != desiredDimensions.GetHeight() )
  {
    // Calculate any padding or cropping that needs to be done based on the fitting mode.
    // Note: If the desired size is larger than the original image, the desired size will be
    // reduced while maintaining the aspect, in order to save unnecessary memory usage.
    int scanlinesToCrop = 0;
    int columnsToCrop = 0;

    CalculateBordersFromFittingMode( ImageDimensions( inputWidth, inputHeight ), fittingMode, desiredDimensions, scanlinesToCrop, columnsToCrop );

    unsigned int desiredWidth( desiredDimensions.GetWidth() );
    unsigned int desiredHeight( desiredDimensions.GetHeight() );

    // Action the changes by making a new bitmap with the central part of the loaded one if required.
    if( scanlinesToCrop != 0 || columnsToCrop != 0 )
    {
      // Split the adding and removing of scanlines and columns into separate variables,
      // so we can use one piece of generic code to action the changes.
      unsigned int scanlinesToPad = 0;
      unsigned int columnsToPad = 0;
      if( scanlinesToCrop < 0 )
      {
        scanlinesToPad = -scanlinesToCrop;
        scanlinesToCrop = 0;
      }
      if( columnsToCrop < 0 )
      {
        columnsToPad = -columnsToCrop;
        columnsToCrop = 0;
      }

      // If there is no filtering, then the final image size can become very large, exit if larger than maximum.
      if( ( desiredWidth > MAXIMUM_TARGET_BITMAP_SIZE ) || ( desiredHeight > MAXIMUM_TARGET_BITMAP_SIZE ) ||
          ( columnsToPad > MAXIMUM_TARGET_BITMAP_SIZE ) || ( scanlinesToPad > MAXIMUM_TARGET_BITMAP_SIZE ) )
      {
        DALI_LOG_WARNING( "Image scaling aborted as final dimensions too large (%u, %u).\n", desiredWidth, desiredHeight );
        return bitmap;
      }

      // Create new PixelBuffer with the desired size.
      const auto pixelFormat = bitmap.GetPixelFormat();

      auto croppedBitmap = Devel::PixelBuffer::New( desiredWidth, desiredHeight, pixelFormat );

      // Add some pre-calculated offsets to the bitmap pointers so this is not done within a loop.
      // The cropping is added to the source pointer, and the padding is added to the destination.
      const auto bytesPerPixel = Pixel::GetBytesPerPixel( pixelFormat );
      const PixelBuffer * const sourcePixels = bitmap.GetBuffer() + ( ( ( ( scanlinesToCrop / 2 ) * inputWidth ) + ( columnsToCrop / 2 ) ) * bytesPerPixel );
      PixelBuffer * const targetPixels = croppedBitmap.GetBuffer();
      PixelBuffer * const targetPixelsActive = targetPixels + ( ( ( ( scanlinesToPad / 2 ) * desiredWidth ) + ( columnsToPad / 2 ) ) * bytesPerPixel );
      DALI_ASSERT_DEBUG( sourcePixels && targetPixels );

      // Copy the image data to the new bitmap.
      // Optimize to a single memcpy if the left and right edges don't need a crop or a pad.
      unsigned int outputSpan( desiredWidth * bytesPerPixel );
      if( columnsToCrop == 0 && columnsToPad == 0 )
      {
        memcpy( targetPixelsActive, sourcePixels, ( desiredHeight - scanlinesToPad ) * outputSpan );
      }
      else
      {
        // The width needs to change (due to either a crop or a pad), so we copy a scanline at a time.
        // Precalculate any constants to optimize the inner loop.
        const unsigned int inputSpan( inputWidth * bytesPerPixel );
        const unsigned int copySpan( ( desiredWidth - columnsToPad ) * bytesPerPixel );
        const unsigned int scanlinesToCopy( desiredHeight - scanlinesToPad );

        for( unsigned int y = 0; y < scanlinesToCopy; ++y )
        {
          memcpy( &targetPixelsActive[ y * outputSpan ], &sourcePixels[ y * inputSpan ], copySpan );
        }
      }

      // Add vertical or horizontal borders to the final image (if required).
      desiredDimensions.SetWidth( desiredWidth );
      desiredDimensions.SetHeight( desiredHeight );
      AddBorders( croppedBitmap.GetBuffer(), bytesPerPixel, desiredDimensions, ImageDimensions( columnsToPad, scanlinesToPad ) );
      // Overwrite the loaded bitmap with the cropped version
      bitmap = croppedBitmap;
    }
  }

  return bitmap;
}

void AddBorders( PixelBuffer *targetPixels, const unsigned int bytesPerPixel, const ImageDimensions targetDimensions, const ImageDimensions padDimensions )
{
  // Assign ints for faster access.
  unsigned int desiredWidth( targetDimensions.GetWidth() );
  unsigned int desiredHeight( targetDimensions.GetHeight() );
  unsigned int columnsToPad( padDimensions.GetWidth() );
  unsigned int scanlinesToPad( padDimensions.GetHeight() );
  unsigned int outputSpan( desiredWidth * bytesPerPixel );

  // Add letterboxing (symmetrical borders) if needed.
  if( scanlinesToPad > 0 )
  {
    // Add a top border. Note: This is (deliberately) rounded down if padding is an odd number.
    memset( targetPixels, BORDER_FILL_VALUE, ( scanlinesToPad / 2 ) * outputSpan );

    // We subtract scanlinesToPad/2 from scanlinesToPad so that we have the correct
    // offset for odd numbers (as the top border is 1 pixel smaller in these cases.
    unsigned int bottomBorderHeight = scanlinesToPad - ( scanlinesToPad / 2 );

    // Bottom border.
    memset( &targetPixels[ ( desiredHeight - bottomBorderHeight ) * outputSpan ], BORDER_FILL_VALUE, bottomBorderHeight * outputSpan );
  }
  else if( columnsToPad > 0 )
  {
    // Add a left and right border.
    // Left:
    // Pre-calculate span size outside of loop.
    unsigned int leftBorderSpanWidth( ( columnsToPad / 2 ) * bytesPerPixel );
    for( unsigned int y = 0; y < desiredHeight; ++y )
    {
      memset( &targetPixels[ y * outputSpan ], BORDER_FILL_VALUE, leftBorderSpanWidth );
    }

    // Right:
    // Pre-calculate the initial x offset as it is always the same for a small optimization.
    // We subtract columnsToPad/2 from columnsToPad so that we have the correct
    // offset for odd numbers (as the left border is 1 pixel smaller in these cases.
    unsigned int rightBorderWidth = columnsToPad - ( columnsToPad / 2 );
    PixelBuffer * const destPixelsRightBorder( targetPixels + ( ( desiredWidth - rightBorderWidth ) * bytesPerPixel ) );
    unsigned int rightBorderSpanWidth = rightBorderWidth * bytesPerPixel;

    for( unsigned int y = 0; y < desiredHeight; ++y )
    {
      memset( &destPixelsRightBorder[ y * outputSpan ], BORDER_FILL_VALUE, rightBorderSpanWidth );
    }
  }
}

Dali::Devel::PixelBuffer DownscaleBitmap( Dali::Devel::PixelBuffer bitmap,
                                        ImageDimensions desired,
                                        FittingMode::Type fittingMode,
                                        SamplingMode::Type samplingMode )
{
  // Source dimensions as loaded from resources (e.g. filesystem):
  auto bitmapWidth  = bitmap.GetWidth();
  auto bitmapHeight = bitmap.GetHeight();
  // Desired dimensions (the rectangle to fit the source image to):
  auto desiredWidth = desired.GetWidth();
  auto desiredHeight = desired.GetHeight();

  Dali::Devel::PixelBuffer outputBitmap { bitmap };

  // If a different size than the raw one has been requested, resize the image:
  if(
      (desiredWidth > 0.0f) && (desiredHeight > 0.0f) &&
      ((desiredWidth < bitmapWidth) || (desiredHeight < bitmapHeight)) )
  {
    auto pixelFormat = bitmap.GetPixelFormat();

    // Do the fast power of 2 iterated box filter to get to roughly the right side if the filter mode requests that:
    unsigned int shrunkWidth = -1, shrunkHeight = -1;
    DownscaleInPlacePow2( bitmap.GetBuffer(), pixelFormat, bitmapWidth, bitmapHeight, desiredWidth, desiredHeight, fittingMode, samplingMode, shrunkWidth, shrunkHeight );

    // Work out the dimensions of the downscaled bitmap, given the scaling mode and desired dimensions:
    const ImageDimensions filteredDimensions = FitToScalingMode( ImageDimensions( desiredWidth, desiredHeight ), ImageDimensions( shrunkWidth, shrunkHeight ), fittingMode );
    const unsigned int filteredWidth = filteredDimensions.GetWidth();
    const unsigned int filteredHeight = filteredDimensions.GetHeight();

    // Run a filter to scale down the bitmap if it needs it:
    bool filtered = false;
    if( filteredWidth < shrunkWidth || filteredHeight < shrunkHeight )
    {
      if( samplingMode == SamplingMode::LINEAR || samplingMode == SamplingMode::BOX_THEN_LINEAR ||
          samplingMode == SamplingMode::NEAREST || samplingMode == SamplingMode::BOX_THEN_NEAREST )
      {
        outputBitmap = Dali::Devel::PixelBuffer::New( filteredWidth, filteredHeight, pixelFormat );

        if( outputBitmap )
        {
          if( samplingMode == SamplingMode::LINEAR || samplingMode == SamplingMode::BOX_THEN_LINEAR )
          {
            LinearSample( bitmap.GetBuffer(), ImageDimensions(shrunkWidth, shrunkHeight), pixelFormat, outputBitmap.GetBuffer(), filteredDimensions );
          }
          else
          {
            PointSample( bitmap.GetBuffer(), shrunkWidth, shrunkHeight, pixelFormat, outputBitmap.GetBuffer(), filteredWidth, filteredHeight );
          }
          filtered = true;
        }
      }
    }
    // Copy out the 2^x downscaled, box-filtered pixels if no secondary filter (point or linear) was applied:
    if( filtered == false && ( shrunkWidth < bitmapWidth || shrunkHeight < bitmapHeight ) )
    {
      outputBitmap = MakePixelBuffer( bitmap.GetBuffer(), pixelFormat, shrunkWidth, shrunkHeight );
    }
  }

  return outputBitmap;
}

namespace
{
/**
 * @brief Returns whether to keep box filtering based on whether downscaled dimensions will overshoot the desired ones aty the next step.
 * @param test Which combination of the two dimensions matter for terminating the filtering.
 * @param scaledWidth The width of the current downscaled image.
 * @param scaledHeight The height of the current downscaled image.
 * @param desiredWidth The target width for the downscaling.
 * @param desiredHeight The target height for the downscaling.
 */
bool ContinueScaling( BoxDimensionTest test, unsigned int scaledWidth, unsigned int scaledHeight, unsigned int desiredWidth, unsigned int desiredHeight )
{
  bool keepScaling = false;
  const unsigned int nextWidth = scaledWidth >> 1u;
  const unsigned int nextHeight = scaledHeight >> 1u;

  if( nextWidth >= 1u && nextHeight >= 1u )
  {
    switch( test )
    {
      case BoxDimensionTestEither:
      {
        keepScaling = nextWidth >= desiredWidth || nextHeight >= desiredHeight;
        break;
      }
      case BoxDimensionTestBoth:
      {
        keepScaling = nextWidth >= desiredWidth && nextHeight >= desiredHeight;
        break;
      }
      case BoxDimensionTestX:
      {
        keepScaling = nextWidth >= desiredWidth;
        break;
      }
      case BoxDimensionTestY:
      {
        keepScaling = nextHeight >= desiredHeight;
        break;
      }
    }
  }

  return keepScaling;
}

/**
 * @brief A shared implementation of the overall iterative box filter
 * downscaling algorithm.
 *
 * Specialise this for particular pixel formats by supplying the number of bytes
 * per pixel and two functions: one for averaging pairs of neighbouring pixels
 * on a single scanline, and a second for averaging pixels at corresponding
 * positions on different scanlines.
 **/
template<
  int BYTES_PER_PIXEL,
  void (*HalveScanlineInPlace)( unsigned char * const pixels, const unsigned int width ),
  void (*AverageScanlines) ( const unsigned char * const scanline1, const unsigned char * const __restrict__ scanline2, unsigned char* const outputScanline, const unsigned int width )
>
void DownscaleInPlacePow2Generic( unsigned char * const pixels,
                                  const unsigned int inputWidth,
                                  const unsigned int inputHeight,
                                  const unsigned int desiredWidth,
                                  const unsigned int desiredHeight,
                                  BoxDimensionTest dimensionTest,
                                  unsigned& outWidth,
                                  unsigned& outHeight )
{
  if( pixels == 0 )
  {
    return;
  }
  ValidateScalingParameters( inputWidth, inputHeight, desiredWidth, desiredHeight );

  // Scale the image until it would be smaller than desired, stopping if the
  // resulting height or width would be less than 1:
  unsigned int scaledWidth = inputWidth, scaledHeight = inputHeight;
  while( ContinueScaling( dimensionTest, scaledWidth, scaledHeight, desiredWidth, desiredHeight ) )
  {
    const unsigned int lastWidth = scaledWidth;
    scaledWidth  >>= 1u;
    scaledHeight >>= 1u;

    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Scaling to %u\t%u.\n", scaledWidth, scaledHeight );

    const unsigned int lastScanlinePair = scaledHeight - 1;

    // Scale pairs of scanlines until any spare one at the end is dropped:
    for( unsigned int y = 0; y <= lastScanlinePair; ++y )
    {
      // Scale two scanlines horizontally:
      HalveScanlineInPlace( &pixels[y * 2 * lastWidth * BYTES_PER_PIXEL], lastWidth );
      HalveScanlineInPlace( &pixels[(y * 2 + 1) * lastWidth * BYTES_PER_PIXEL], lastWidth );

      // Scale vertical pairs of pixels while the last two scanlines are still warm in
      // the CPU cache(s):
      // Note, better access patterns for cache-coherence are possible for very large
      // images but even a 4k wide RGB888 image will use just 24kB of cache (4k pixels
      // * 3 Bpp * 2 scanlines) for two scanlines on the first iteration.
      AverageScanlines(
          &pixels[y * 2 * lastWidth * BYTES_PER_PIXEL],
          &pixels[(y * 2 + 1) * lastWidth * BYTES_PER_PIXEL],
          &pixels[y * scaledWidth * BYTES_PER_PIXEL],
          scaledWidth );
    }
  }

  ///@note: we could finish off with one of two mutually exclusive passes, one squashing horizontally as far as possible, and the other vertically, if we knew a following cpu point or bilinear filter would restore the desired aspect ratio.
  outWidth = scaledWidth;
  outHeight = scaledHeight;
}

}

void HalveScanlineInPlaceRGB888( unsigned char * const pixels, const unsigned int width )
{
  DebugAssertScanlineParameters( pixels, width );

  const unsigned int lastPair = EvenDown( width - 2 );

  for( unsigned int pixel = 0, outPixel = 0; pixel <= lastPair; pixel += 2, ++outPixel )
  {
    // Load all the byte pixel components we need:
    const unsigned int c11 = pixels[pixel * 3];
    const unsigned int c12 = pixels[pixel * 3 + 1];
    const unsigned int c13 = pixels[pixel * 3 + 2];
    const unsigned int c21 = pixels[pixel * 3 + 3];
    const unsigned int c22 = pixels[pixel * 3 + 4];
    const unsigned int c23 = pixels[pixel * 3 + 5];

    // Save the averaged byte pixel components:
    pixels[outPixel * 3]     = AverageComponent( c11, c21 );
    pixels[outPixel * 3 + 1] = AverageComponent( c12, c22 );
    pixels[outPixel * 3 + 2] = AverageComponent( c13, c23 );
  }
}

void HalveScanlineInPlaceRGBA8888( unsigned char * const pixels, const unsigned int width )
{
  DebugAssertScanlineParameters( pixels, width );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(pixels) & 3u) == 0u) && "Pointer should be 4-byte aligned for performance on some platforms." );

  uint32_t* const alignedPixels = reinterpret_cast<uint32_t*>(pixels);

  const unsigned int lastPair = EvenDown( width - 2 );

  for( unsigned int pixel = 0, outPixel = 0; pixel <= lastPair; pixel += 2, ++outPixel )
  {
    const uint32_t averaged = AveragePixelRGBA8888( alignedPixels[pixel], alignedPixels[pixel + 1] );
    alignedPixels[outPixel] = averaged;
  }
}

void HalveScanlineInPlaceRGB565( unsigned char * pixels, unsigned int width )
{
  DebugAssertScanlineParameters( pixels, width );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(pixels) & 1u) == 0u) && "Pointer should be 2-byte aligned for performance on some platforms." );

  uint16_t* const alignedPixels = reinterpret_cast<uint16_t*>(pixels);

  const unsigned int lastPair = EvenDown( width - 2 );

  for( unsigned int pixel = 0, outPixel = 0; pixel <= lastPair; pixel += 2, ++outPixel )
  {
    const uint32_t averaged = AveragePixelRGB565( alignedPixels[pixel], alignedPixels[pixel + 1] );
    alignedPixels[outPixel] = averaged;
  }
}

void HalveScanlineInPlace2Bytes( unsigned char * const pixels, const unsigned int width )
{
  DebugAssertScanlineParameters( pixels, width );

  const unsigned int lastPair = EvenDown( width - 2 );

  for( unsigned int pixel = 0, outPixel = 0; pixel <= lastPair; pixel += 2, ++outPixel )
  {
    // Load all the byte pixel components we need:
    const unsigned int c11 = pixels[pixel * 2];
    const unsigned int c12 = pixels[pixel * 2 + 1];
    const unsigned int c21 = pixels[pixel * 2 + 2];
    const unsigned int c22 = pixels[pixel * 2 + 3];

    // Save the averaged byte pixel components:
    pixels[outPixel * 2]     = AverageComponent( c11, c21 );
    pixels[outPixel * 2 + 1] = AverageComponent( c12, c22 );
  }
}

void HalveScanlineInPlace1Byte( unsigned char * const pixels, const unsigned int width )
{
  DebugAssertScanlineParameters( pixels, width );

  const unsigned int lastPair = EvenDown( width - 2 );

  for( unsigned int pixel = 0, outPixel = 0; pixel <= lastPair; pixel += 2, ++outPixel )
  {
    // Load all the byte pixel components we need:
    const unsigned int c1 = pixels[pixel];
    const unsigned int c2 = pixels[pixel + 1];

    // Save the averaged byte pixel component:
    pixels[outPixel] = AverageComponent( c1, c2 );
  }
}

/**
 * @ToDo: Optimise for ARM using a 4 bytes at a time loop wrapped around the single ARMV6 instruction: UHADD8  R4, R0, R5. Note, this is not neon. It runs in the normal integer pipeline so there is no downside like a stall moving between integer and copro, or extra power for clocking-up the idle copro.
 * if (widthInComponents >= 7) { word32* aligned1 = scanline1 + 3 & 3; word32* aligned1_end = scanline1 + widthInPixels & 3; while(aligned1 < aligned1_end) { UHADD8  *aligned1++, *aligned2++, *alignedoutput++ } .. + 0 to 3 spare pixels at each end.
 */
void AverageScanlines1( const unsigned char * const scanline1,
                        const unsigned char * const __restrict__ scanline2,
                        unsigned char* const outputScanline,
                        const unsigned int width )
{
  DebugAssertDualScanlineParameters( scanline1, scanline2, outputScanline, width );

  for( unsigned int component = 0; component < width; ++component )
  {
    outputScanline[component] = AverageComponent( scanline1[component], scanline2[component] );
  }
}

void AverageScanlines2( const unsigned char * const scanline1,
                        const unsigned char * const __restrict__ scanline2,
                        unsigned char* const outputScanline,
                        const unsigned int width )
{
  DebugAssertDualScanlineParameters( scanline1, scanline2, outputScanline, width * 2 );

  for( unsigned int component = 0; component < width * 2; ++component )
  {
    outputScanline[component] = AverageComponent( scanline1[component], scanline2[component] );
  }
}

void AverageScanlines3( const unsigned char * const scanline1,
                        const unsigned char * const __restrict__ scanline2,
                        unsigned char* const outputScanline,
                        const unsigned int width )
{
  DebugAssertDualScanlineParameters( scanline1, scanline2, outputScanline, width * 3 );

  for( unsigned int component = 0; component < width * 3; ++component )
  {
    outputScanline[component] = AverageComponent( scanline1[component], scanline2[component] );
  }
}

void AverageScanlinesRGBA8888( const unsigned char * const scanline1,
                               const unsigned char * const __restrict__ scanline2,
                               unsigned char * const outputScanline,
                               const unsigned int width )
{
  DebugAssertDualScanlineParameters( scanline1, scanline2, outputScanline, width * 4 );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(scanline1) & 3u) == 0u) && "Pointer should be 4-byte aligned for performance on some platforms." );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(scanline2) & 3u) == 0u) && "Pointer should be 4-byte aligned for performance on some platforms." );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(outputScanline) & 3u) == 0u) && "Pointer should be 4-byte aligned for performance on some platforms." );

  const uint32_t* const alignedScanline1 = reinterpret_cast<const uint32_t*>(scanline1);
  const uint32_t* const alignedScanline2 = reinterpret_cast<const uint32_t*>(scanline2);
  uint32_t* const alignedOutput = reinterpret_cast<uint32_t*>(outputScanline);

  for( unsigned int pixel = 0; pixel < width; ++pixel )
  {
    alignedOutput[pixel] = AveragePixelRGBA8888( alignedScanline1[pixel], alignedScanline2[pixel] );
  }
}

void AverageScanlinesRGB565( const unsigned char * const scanline1,
                             const unsigned char * const __restrict__ scanline2,
                             unsigned char * const outputScanline,
                             const unsigned int width )
{
  DebugAssertDualScanlineParameters( scanline1, scanline2, outputScanline, width * 2 );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(scanline1) & 1u) == 0u) && "Pointer should be 2-byte aligned for performance on some platforms." );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(scanline2) & 1u) == 0u) && "Pointer should be 2-byte aligned for performance on some platforms." );
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(outputScanline) & 1u) == 0u) && "Pointer should be 2-byte aligned for performance on some platforms." );

  const uint16_t* const alignedScanline1 = reinterpret_cast<const uint16_t*>(scanline1);
  const uint16_t* const alignedScanline2 = reinterpret_cast<const uint16_t*>(scanline2);
  uint16_t* const alignedOutput = reinterpret_cast<uint16_t*>(outputScanline);

  for( unsigned int pixel = 0; pixel < width; ++pixel )
  {
    alignedOutput[pixel] = AveragePixelRGB565( alignedScanline1[pixel], alignedScanline2[pixel] );
  }
}

/// Dispatch to pixel format appropriate box filter downscaling functions.
void DownscaleInPlacePow2( unsigned char * const pixels,
                           Pixel::Format pixelFormat,
                           unsigned int inputWidth,
                           unsigned int inputHeight,
                           unsigned int desiredWidth,
                           unsigned int desiredHeight,
                           FittingMode::Type fittingMode,
                           SamplingMode::Type samplingMode,
                           unsigned& outWidth,
                           unsigned& outHeight )
{
  outWidth = inputWidth;
  outHeight = inputHeight;
  // Perform power of 2 iterated 4:1 box filtering if the requested filter mode requires it:
  if( samplingMode == SamplingMode::BOX || samplingMode == SamplingMode::BOX_THEN_NEAREST || samplingMode == SamplingMode::BOX_THEN_LINEAR )
  {
    // Check the pixel format is one that is supported:
    if( pixelFormat == Pixel::RGBA8888 || pixelFormat == Pixel::RGB888 || pixelFormat == Pixel::RGB565 || pixelFormat == Pixel::LA88 || pixelFormat == Pixel::L8 || pixelFormat == Pixel::A8 )
    {
      const BoxDimensionTest dimensionTest = DimensionTestForScalingMode( fittingMode );

      if( pixelFormat == Pixel::RGBA8888 )
      {
        Internal::Platform::DownscaleInPlacePow2RGBA8888( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
      }
      else if( pixelFormat == Pixel::RGB888 )
      {
        Internal::Platform::DownscaleInPlacePow2RGB888( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
      }
      else if( pixelFormat == Pixel::RGB565 )
      {
        Internal::Platform::DownscaleInPlacePow2RGB565( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
      }
      else if( pixelFormat == Pixel::LA88 )
      {
        Internal::Platform::DownscaleInPlacePow2ComponentPair( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
      }
      else if( pixelFormat == Pixel::L8  || pixelFormat == Pixel::A8 )
      {
        Internal::Platform::DownscaleInPlacePow2SingleBytePerPixel( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
      }
      else
      {
        DALI_ASSERT_DEBUG( false == "Inner branch conditions don't match outer branch." );
      }
    }
  }
  else
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Bitmap was not shrunk: unsupported pixel format: %u.\n", unsigned(pixelFormat) );
  }
}

void DownscaleInPlacePow2RGB888( unsigned char *pixels,
                                 unsigned int inputWidth,
                                 unsigned int inputHeight,
                                 unsigned int desiredWidth,
                                 unsigned int desiredHeight,
                                 BoxDimensionTest dimensionTest,
                                 unsigned& outWidth,
                                 unsigned& outHeight )
{
  DownscaleInPlacePow2Generic<3, HalveScanlineInPlaceRGB888, AverageScanlines3>( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
}

void DownscaleInPlacePow2RGBA8888( unsigned char * pixels,
                                   unsigned int inputWidth,
                                   unsigned int inputHeight,
                                   unsigned int desiredWidth,
                                   unsigned int desiredHeight,
                                   BoxDimensionTest dimensionTest,
                                   unsigned& outWidth,
                                   unsigned& outHeight )
{
  DALI_ASSERT_DEBUG( ((reinterpret_cast<ptrdiff_t>(pixels) & 3u) == 0u) && "Pointer should be 4-byte aligned for performance on some platforms." );
  DownscaleInPlacePow2Generic<4, HalveScanlineInPlaceRGBA8888, AverageScanlinesRGBA8888>( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
}

void DownscaleInPlacePow2RGB565( unsigned char * pixels,
                                 unsigned int inputWidth,
                                 unsigned int inputHeight,
                                 unsigned int desiredWidth,
                                 unsigned int desiredHeight,
                                 BoxDimensionTest dimensionTest,
                                 unsigned int& outWidth,
                                 unsigned int& outHeight )
{
  DownscaleInPlacePow2Generic<2, HalveScanlineInPlaceRGB565, AverageScanlinesRGB565>( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
}

/**
 * @copydoc DownscaleInPlacePow2RGB888
 *
 * For 2-byte formats such as lum8alpha8, but not packed 16 bit formats like RGB565.
 */
void DownscaleInPlacePow2ComponentPair( unsigned char *pixels,
                                        unsigned int inputWidth,
                                        unsigned int inputHeight,
                                        unsigned int desiredWidth,
                                        unsigned int desiredHeight,
                                        BoxDimensionTest dimensionTest,
                                        unsigned& outWidth,
                                        unsigned& outHeight )
{
  DownscaleInPlacePow2Generic<2, HalveScanlineInPlace2Bytes, AverageScanlines2>( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
}

void DownscaleInPlacePow2SingleBytePerPixel( unsigned char * pixels,
                                             unsigned int inputWidth,
                                             unsigned int inputHeight,
                                             unsigned int desiredWidth,
                                             unsigned int desiredHeight,
                                             BoxDimensionTest dimensionTest,
                                             unsigned int& outWidth,
                                             unsigned int& outHeight )
{
  DownscaleInPlacePow2Generic<1, HalveScanlineInPlace1Byte, AverageScanlines1>( pixels, inputWidth, inputHeight, desiredWidth, desiredHeight, dimensionTest, outWidth, outHeight );
}

namespace
{

/**
 * @brief Point sample an image to a new resolution (like GL_NEAREST).
 *
 * Template is used purely as a type-safe code generator in this one
 * compilation unit. Generated code is inlined into type-specific wrapper
 * functions below which are exported to rest of module.
 */
template<typename PIXEL>
inline void PointSampleAddressablePixels( const uint8_t * inPixels,
                                   unsigned int inputWidth,
                                   unsigned int inputHeight,
                                   uint8_t * outPixels,
                                   unsigned int desiredWidth,
                                   unsigned int desiredHeight )
{
  DALI_ASSERT_DEBUG( ((desiredWidth <= inputWidth && desiredHeight <= inputHeight) ||
      outPixels >= inPixels + inputWidth * inputHeight * sizeof(PIXEL) || outPixels <= inPixels - desiredWidth * desiredHeight * sizeof(PIXEL)) &&
      "The input and output buffers must not overlap for an upscaling.");
  DALI_ASSERT_DEBUG( reinterpret_cast< uint64_t >( inPixels )  % sizeof(PIXEL) == 0 && "Pixel pointers need to be aligned to the size of the pixels (E.g., 4 bytes for RGBA, 2 bytes for RGB565, ...)." );
  DALI_ASSERT_DEBUG( reinterpret_cast< uint64_t >( outPixels ) % sizeof(PIXEL) == 0 && "Pixel pointers need to be aligned to the size of the pixels (E.g., 4 bytes for RGBA, 2 bytes for RGB565, ...)." );

  if( inputWidth < 1u || inputHeight < 1u || desiredWidth < 1u || desiredHeight < 1u )
  {
    return;
  }
  const PIXEL* const inAligned = reinterpret_cast<const PIXEL*>(inPixels);
  PIXEL* const       outAligned = reinterpret_cast<PIXEL*>(outPixels);
  const unsigned int deltaX = (inputWidth  << 16u) / desiredWidth;
  const unsigned int deltaY = (inputHeight << 16u) / desiredHeight;

  unsigned int inY = 0;
  for( unsigned int outY = 0; outY < desiredHeight; ++outY )
  {
    // Round fixed point y coordinate to nearest integer:
    const unsigned int integerY = (inY + (1u << 15u)) >> 16u;
    const PIXEL* const inScanline = &inAligned[inputWidth * integerY];
    PIXEL* const outScanline = &outAligned[desiredWidth * outY];

    DALI_ASSERT_DEBUG( integerY < inputHeight );
    DALI_ASSERT_DEBUG( reinterpret_cast<const uint8_t*>(inScanline) < ( inPixels + inputWidth * inputHeight * sizeof(PIXEL) ) );
    DALI_ASSERT_DEBUG( reinterpret_cast<uint8_t*>(outScanline) < ( outPixels + desiredWidth * desiredHeight * sizeof(PIXEL) ) );

    unsigned int inX = 0;
    for( unsigned int outX = 0; outX < desiredWidth; ++outX )
    {
      // Round the fixed-point x coordinate to an integer:
      const unsigned int integerX = (inX + (1u << 15u)) >> 16u;
      const PIXEL* const inPixelAddress = &inScanline[integerX];
      const PIXEL pixel = *inPixelAddress;
      outScanline[outX] = pixel;
      inX += deltaX;
    }
    inY += deltaY;
  }
}

}

// RGBA8888
void PointSample4BPP( const unsigned char * inPixels,
                      unsigned int inputWidth,
                      unsigned int inputHeight,
                      unsigned char * outPixels,
                      unsigned int desiredWidth,
                      unsigned int desiredHeight )
{
  PointSampleAddressablePixels<uint32_t>( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
}

// RGB565, LA88
void PointSample2BPP( const unsigned char * inPixels,
                      unsigned int inputWidth,
                      unsigned int inputHeight,
                      unsigned char * outPixels,
                      unsigned int desiredWidth,
                      unsigned int desiredHeight )
{
  PointSampleAddressablePixels<uint16_t>( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
}

// L8, A8
void PointSample1BPP( const unsigned char * inPixels,
                      unsigned int inputWidth,
                      unsigned int inputHeight,
                      unsigned char * outPixels,
                      unsigned int desiredWidth,
                      unsigned int desiredHeight )
{
  PointSampleAddressablePixels<uint8_t>( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
}

/* RGB888
 * RGB888 is a special case as its pixels are not aligned addressable units.
 */
void PointSample3BPP( const uint8_t * inPixels,
                      unsigned int inputWidth,
                      unsigned int inputHeight,
                      uint8_t * outPixels,
                      unsigned int desiredWidth,
                      unsigned int desiredHeight )
{
  if( inputWidth < 1u || inputHeight < 1u || desiredWidth < 1u || desiredHeight < 1u )
  {
    return;
  }
  const unsigned int BYTES_PER_PIXEL = 3;

  // Generate fixed-point 16.16 deltas in input image coordinates:
  const unsigned int deltaX = (inputWidth  << 16u) / desiredWidth;
  const unsigned int deltaY = (inputHeight << 16u) / desiredHeight;

  // Step through output image in whole integer pixel steps while tracking the
  // corresponding locations in the input image using 16.16 fixed-point
  // coordinates:
  unsigned int inY = 0; //< 16.16 fixed-point input image y-coord.
  for( unsigned int outY = 0; outY < desiredHeight; ++outY )
  {
    const unsigned int integerY = (inY + (1u << 15u)) >> 16u;
    const uint8_t* const inScanline = &inPixels[inputWidth * integerY * BYTES_PER_PIXEL];
    uint8_t* const outScanline = &outPixels[desiredWidth * outY * BYTES_PER_PIXEL];
    unsigned int inX = 0; //< 16.16 fixed-point input image x-coord.

    for( unsigned int outX = 0; outX < desiredWidth * BYTES_PER_PIXEL; outX += BYTES_PER_PIXEL )
    {
      // Round the fixed-point input coordinate to the address of the input pixel to sample:
      const unsigned int integerX = (inX + (1u << 15u)) >> 16u;
      const uint8_t* const inPixelAddress = &inScanline[integerX * BYTES_PER_PIXEL];

      // Issue loads for all pixel color components up-front:
      const unsigned int c0 = inPixelAddress[0];
      const unsigned int c1 = inPixelAddress[1];
      const unsigned int c2 = inPixelAddress[2];
      ///@ToDo: Optimise - Benchmark one 32bit load that will be unaligned 2/3 of the time + 3 rotate and masks, versus these three aligned byte loads, versus using an RGB packed, aligned(1) struct and letting compiler pick a strategy.

      // Output the pixel components:
      outScanline[outX]     = c0;
      outScanline[outX + 1] = c1;
      outScanline[outX + 2] = c2;

      // Increment the fixed-point input coordinate:
      inX += deltaX;
    }

    inY += deltaY;
  }
}

// Dispatch to a format-appropriate point sampling function:
void PointSample( const unsigned char * inPixels,
                  unsigned int inputWidth,
                  unsigned int inputHeight,
                  Pixel::Format pixelFormat,
                  unsigned char * outPixels,
                  unsigned int desiredWidth,
                  unsigned int desiredHeight )
{
  // Check the pixel format is one that is supported:
  if( pixelFormat == Pixel::RGBA8888 || pixelFormat == Pixel::RGB888 || pixelFormat == Pixel::RGB565 || pixelFormat == Pixel::LA88 || pixelFormat == Pixel::L8 || pixelFormat == Pixel::A8 )
  {
    if( pixelFormat == Pixel::RGB888 )
    {
      PointSample3BPP( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
    }
    else if( pixelFormat == Pixel::RGBA8888 )
    {
      PointSample4BPP( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
    }
    else if( pixelFormat == Pixel::RGB565 || pixelFormat == Pixel::LA88 )
    {
      PointSample2BPP( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
    }
    else if( pixelFormat == Pixel::L8  || pixelFormat == Pixel::A8 )
    {
      PointSample1BPP( inPixels, inputWidth, inputHeight, outPixels, desiredWidth, desiredHeight );
    }
    else
    {
      DALI_ASSERT_DEBUG( false == "Inner branch conditions don't match outer branch." );
    }
  }
  else
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Bitmap was not point sampled: unsupported pixel format: %u.\n", unsigned(pixelFormat) );
  }
}

// Linear sampling group below

namespace
{

/** @brief Blend 4 pixels together using horizontal and vertical weights. */
inline uint8_t BilinearFilter1BPPByte( uint8_t tl, uint8_t tr, uint8_t bl, uint8_t br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical )
{
  return BilinearFilter1Component( tl, tr, bl, br, fractBlendHorizontal, fractBlendVertical );
}

/** @copydoc BilinearFilter1BPPByte */
inline Pixel2Bytes BilinearFilter2Bytes( Pixel2Bytes tl, Pixel2Bytes tr, Pixel2Bytes bl, Pixel2Bytes br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical )
{
  Pixel2Bytes pixel;
  pixel.l = BilinearFilter1Component( tl.l, tr.l, bl.l, br.l, fractBlendHorizontal, fractBlendVertical );
  pixel.a = BilinearFilter1Component( tl.a, tr.a, bl.a, br.a, fractBlendHorizontal, fractBlendVertical );
  return pixel;
}

/** @copydoc BilinearFilter1BPPByte */
inline Pixel3Bytes BilinearFilterRGB888( Pixel3Bytes tl, Pixel3Bytes tr, Pixel3Bytes bl, Pixel3Bytes br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical )
{
  Pixel3Bytes pixel;
  pixel.r = BilinearFilter1Component( tl.r, tr.r, bl.r, br.r, fractBlendHorizontal, fractBlendVertical );
  pixel.g = BilinearFilter1Component( tl.g, tr.g, bl.g, br.g, fractBlendHorizontal, fractBlendVertical );
  pixel.b = BilinearFilter1Component( tl.b, tr.b, bl.b, br.b, fractBlendHorizontal, fractBlendVertical );
  return pixel;
}

/** @copydoc BilinearFilter1BPPByte */
inline PixelRGB565 BilinearFilterRGB565( PixelRGB565 tl, PixelRGB565 tr, PixelRGB565 bl, PixelRGB565 br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical )
{
  const PixelRGB565 pixel = (BilinearFilter1Component( tl >> 11u, tr >> 11u, bl >> 11u, br >> 11u, fractBlendHorizontal, fractBlendVertical ) << 11u) +
                            (BilinearFilter1Component( (tl >> 5u) & 63u, (tr >> 5u) & 63u, (bl >> 5u) & 63u, (br >> 5u) & 63u, fractBlendHorizontal, fractBlendVertical ) << 5u) +
                             BilinearFilter1Component( tl & 31u, tr & 31u, bl & 31u, br & 31u, fractBlendHorizontal, fractBlendVertical );
  return pixel;
}

/** @copydoc BilinearFilter1BPPByte */
inline Pixel4Bytes BilinearFilter4Bytes( Pixel4Bytes tl, Pixel4Bytes tr, Pixel4Bytes bl, Pixel4Bytes br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical )
{
  Pixel4Bytes pixel;
  pixel.r = BilinearFilter1Component( tl.r, tr.r, bl.r, br.r, fractBlendHorizontal, fractBlendVertical );
  pixel.g = BilinearFilter1Component( tl.g, tr.g, bl.g, br.g, fractBlendHorizontal, fractBlendVertical );
  pixel.b = BilinearFilter1Component( tl.b, tr.b, bl.b, br.b, fractBlendHorizontal, fractBlendVertical );
  pixel.a = BilinearFilter1Component( tl.a, tr.a, bl.a, br.a, fractBlendHorizontal, fractBlendVertical );
  return pixel;
}

/**
 * @brief Generic version of bilinear sampling image resize function.
 * @note Limited to one compilation unit and exposed through type-specific
 * wrapper functions below.
 */
template<
  typename PIXEL,
  PIXEL (*BilinearFilter) ( PIXEL tl, PIXEL tr, PIXEL bl, PIXEL br, unsigned int fractBlendHorizontal, unsigned int fractBlendVertical ),
  bool DEBUG_ASSERT_ALIGNMENT
>
inline void LinearSampleGeneric( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  const unsigned int inputWidth = inputDimensions.GetWidth();
  const unsigned int inputHeight = inputDimensions.GetHeight();
  const unsigned int desiredWidth = desiredDimensions.GetWidth();
  const unsigned int desiredHeight = desiredDimensions.GetHeight();

  DALI_ASSERT_DEBUG( ((outPixels >= inPixels + inputWidth   * inputHeight   * sizeof(PIXEL)) ||
                      (inPixels >= outPixels + desiredWidth * desiredHeight * sizeof(PIXEL))) &&
                     "Input and output buffers cannot overlap.");
  if( DEBUG_ASSERT_ALIGNMENT )
  {
    DALI_ASSERT_DEBUG( reinterpret_cast< uint64_t >( inPixels )  % sizeof(PIXEL) == 0 && "Pixel pointers need to be aligned to the size of the pixels (E.g., 4 bytes for RGBA, 2 bytes for RGB565, ...)." );
    DALI_ASSERT_DEBUG( reinterpret_cast< uint64_t >( outPixels) % sizeof(PIXEL) == 0 && "Pixel pointers need to be aligned to the size of the pixels (E.g., 4 bytes for RGBA, 2 bytes for RGB565, ...)." );
  }

  if( inputWidth < 1u || inputHeight < 1u || desiredWidth < 1u || desiredHeight < 1u )
  {
    return;
  }
  const PIXEL* const inAligned = reinterpret_cast<const PIXEL*>(inPixels);
  PIXEL* const       outAligned = reinterpret_cast<PIXEL*>(outPixels);
  const unsigned int deltaX = (inputWidth  << 16u) / desiredWidth;
  const unsigned int deltaY = (inputHeight << 16u) / desiredHeight;

  unsigned int inY = 0;
  for( unsigned int outY = 0; outY < desiredHeight; ++outY )
  {
    PIXEL* const outScanline = &outAligned[desiredWidth * outY];

    // Find the two scanlines to blend and the weight to blend with:
    const unsigned int integerY1 = inY >> 16u;
    const unsigned int integerY2 = integerY1 >= inputHeight ? integerY1 : integerY1 + 1;
    const unsigned int inputYWeight = inY & 65535u;

    DALI_ASSERT_DEBUG( integerY1 < inputHeight );
    DALI_ASSERT_DEBUG( integerY2 < inputHeight );

    const PIXEL* const inScanline1 = &inAligned[inputWidth * integerY1];
    const PIXEL* const inScanline2 = &inAligned[inputWidth * integerY2];

    unsigned int inX = 0;
    for( unsigned int outX = 0; outX < desiredWidth; ++outX )
    {
      // Work out the two pixel scanline offsets for this cluster of four samples:
      const unsigned int integerX1 = inX >> 16u;
      const unsigned int integerX2 = integerX1 >= inputWidth ? integerX1 : integerX1 + 1;

      // Execute the loads:
      const PIXEL pixel1 = inScanline1[integerX1];
      const PIXEL pixel2 = inScanline2[integerX1];
      const PIXEL pixel3 = inScanline1[integerX2];
      const PIXEL pixel4 = inScanline2[integerX2];
      ///@ToDo Optimise - for 1 and 2  and 4 byte types to execute a single 2, 4, or 8 byte load per pair (caveat clamping) and let half of them be unaligned.

      // Weighted bilinear filter:
      const unsigned int inputXWeight = inX & 65535u;
      outScanline[outX] = BilinearFilter( pixel1, pixel3, pixel2, pixel4, inputXWeight, inputYWeight );

      inX += deltaX;
    }
    inY += deltaY;
  }
}

}

// Format-specific linear scaling instantiations:

void LinearSample1BPP( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  LinearSampleGeneric<uint8_t, BilinearFilter1BPPByte, false>( inPixels, inputDimensions, outPixels, desiredDimensions );
}

void LinearSample2BPP( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  LinearSampleGeneric<Pixel2Bytes, BilinearFilter2Bytes, true>( inPixels, inputDimensions, outPixels, desiredDimensions );
}

void LinearSampleRGB565( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  LinearSampleGeneric<PixelRGB565, BilinearFilterRGB565, true>( inPixels, inputDimensions, outPixels, desiredDimensions );
}

void LinearSample3BPP( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  LinearSampleGeneric<Pixel3Bytes, BilinearFilterRGB888, false>( inPixels, inputDimensions, outPixels, desiredDimensions );
}

void LinearSample4BPP( const unsigned char * __restrict__ inPixels,
                       ImageDimensions inputDimensions,
                       unsigned char * __restrict__ outPixels,
                       ImageDimensions desiredDimensions )
{
  LinearSampleGeneric<Pixel4Bytes, BilinearFilter4Bytes, true>( inPixels, inputDimensions, outPixels, desiredDimensions );
}


void Resample( const unsigned char * __restrict__ inPixels,
               ImageDimensions inputDimensions,
               unsigned char * __restrict__ outPixels,
               ImageDimensions desiredDimensions,
               Resampler::Filter filterType,
               int numChannels, bool hasAlpha )
{
  // Got from the test.cpp of the ImageResampler lib.
  const float ONE_DIV_255 = 1.0f / 255.0f;
  const int MAX_UNSIGNED_CHAR = std::numeric_limits<uint8_t>::max();
  const int LINEAR_TO_SRGB_TABLE_SIZE = 4096;
  const int ALPHA_CHANNEL = hasAlpha ? (numChannels-1) : 0;

  static bool loadColorSpaces = true;
  static float srgbToLinear[MAX_UNSIGNED_CHAR + 1];
  static unsigned char linearToSrgb[LINEAR_TO_SRGB_TABLE_SIZE];

  if( loadColorSpaces ) // Only create the color space conversions on the first execution
  {
    loadColorSpaces = false;

    for( int i = 0; i <= MAX_UNSIGNED_CHAR; ++i )
    {
      srgbToLinear[i] = pow( static_cast<float>( i ) * ONE_DIV_255, DEFAULT_SOURCE_GAMMA );
    }

    const float invLinearToSrgbTableSize = 1.0f / static_cast<float>( LINEAR_TO_SRGB_TABLE_SIZE );
    const float invSourceGamma = 1.0f / DEFAULT_SOURCE_GAMMA;

    for( int i = 0; i < LINEAR_TO_SRGB_TABLE_SIZE; ++i )
    {
      int k = static_cast<int>( 255.0f * pow( static_cast<float>( i ) * invLinearToSrgbTableSize, invSourceGamma ) + 0.5f );
      if( k < 0 )
      {
        k = 0;
      }
      else if( k > MAX_UNSIGNED_CHAR )
      {
        k = MAX_UNSIGNED_CHAR;
      }
      linearToSrgb[i] = static_cast<unsigned char>( k );
    }
  }

  Resampler* resamplers[numChannels];
  Vector<float> samples[numChannels];

  const int srcWidth = inputDimensions.GetWidth();
  const int srcHeight = inputDimensions.GetHeight();
  const int dstWidth = desiredDimensions.GetWidth();
  const int dstHeight = desiredDimensions.GetHeight();

  // Now create a Resampler instance for each component to process. The first instance will create new contributor tables, which are shared by the resamplers
  // used for the other components (a memory and slight cache efficiency optimization).
  resamplers[0] = new Resampler( srcWidth,
                                 srcHeight,
                                 dstWidth,
                                 dstHeight,
                                 Resampler::BOUNDARY_CLAMP,
                                 0.0f,           // sample_low,
                                 1.0f,           // sample_high. Clamp output samples to specified range, or disable clamping if sample_low >= sample_high.
                                 filterType,    // The type of filter.
                                 NULL,           // Pclist_x,
                                 NULL,           // Pclist_y. Optional pointers to contributor lists from another instance of a Resampler.
                                 FILTER_SCALE,   // src_x_ofs,
                                 FILTER_SCALE ); // src_y_ofs. Offset input image by specified amount (fractional values okay).
  samples[0].Resize( srcWidth );
  for( int i = 1; i < numChannels; ++i )
  {
    resamplers[i] = new Resampler( srcWidth,
                                   srcHeight,
                                   dstWidth,
                                   dstHeight,
                                   Resampler::BOUNDARY_CLAMP,
                                   0.0f,
                                   1.0f,
                                   filterType,
                                   resamplers[0]->get_clist_x(),
                                   resamplers[0]->get_clist_y(),
                                   FILTER_SCALE,
                                   FILTER_SCALE );
    samples[i].Resize( srcWidth );
  }

  const int srcPitch = srcWidth * numChannels;
  const int dstPitch = dstWidth * numChannels;
  int dstY = 0;

  for( int srcY = 0; srcY < srcHeight; ++srcY )
  {
    const unsigned char* pSrc = &inPixels[srcY * srcPitch];

    for( int x = 0; x < srcWidth; ++x )
    {
      for( int c = 0; c < numChannels; ++c )
      {
        if( c == ALPHA_CHANNEL && hasAlpha )
        {
          samples[c][x] = *pSrc++ * ONE_DIV_255;
        }
        else
        {
          samples[c][x] = srgbToLinear[*pSrc++];
        }
      }
    }

    for( int c = 0; c < numChannels; ++c )
    {
      if( !resamplers[c]->put_line( &samples[c][0] ) )
      {
        DALI_ASSERT_DEBUG( !"Out of memory" );
      }
    }

    for(;;)
    {
      int compIndex;
      for( compIndex = 0; compIndex < numChannels; ++compIndex )
      {
        const float* pOutputSamples = resamplers[compIndex]->get_line();
        if( !pOutputSamples )
        {
          break;
        }

        const bool isAlphaChannel = ( compIndex == ALPHA_CHANNEL && hasAlpha );
        DALI_ASSERT_DEBUG( dstY < dstHeight );
        unsigned char* pDst = &outPixels[dstY * dstPitch + compIndex];

        for( int x = 0; x < dstWidth; ++x )
        {
          if( isAlphaChannel )
          {
            int c = static_cast<int>( 255.0f * pOutputSamples[x] + 0.5f );
            if( c < 0 )
            {
              c = 0;
            }
            else if( c > MAX_UNSIGNED_CHAR )
            {
              c = MAX_UNSIGNED_CHAR;
            }
            *pDst = static_cast<unsigned char>( c );
          }
          else
          {
            int j = static_cast<int>( LINEAR_TO_SRGB_TABLE_SIZE * pOutputSamples[x] + 0.5f );
            if( j < 0 )
            {
              j = 0;
            }
            else if( j >= LINEAR_TO_SRGB_TABLE_SIZE )
            {
              j = LINEAR_TO_SRGB_TABLE_SIZE - 1;
            }
            *pDst = linearToSrgb[j];
          }

          pDst += numChannels;
        }
      }
      if( compIndex < numChannels )
      {
        break;
      }

      ++dstY;
    }
  }

  // Delete the resamplers.
  for( int i = 0; i < numChannels; ++i )
  {
    delete resamplers[i];
  }
}

void LanczosSample4BPP( const unsigned char * __restrict__ inPixels,
                        ImageDimensions inputDimensions,
                        unsigned char * __restrict__ outPixels,
                        ImageDimensions desiredDimensions )
{
  Resample( inPixels, inputDimensions, outPixels, desiredDimensions, Resampler::LANCZOS4, 4, true );
}

void LanczosSample1BPP( const unsigned char * __restrict__ inPixels,
                        ImageDimensions inputDimensions,
                        unsigned char * __restrict__ outPixels,
                        ImageDimensions desiredDimensions )
{
  // For L8 images
  Resample( inPixels, inputDimensions, outPixels, desiredDimensions, Resampler::LANCZOS4, 1, false );
}

// Dispatch to a format-appropriate linear sampling function:
void LinearSample( const unsigned char * __restrict__ inPixels,
                   ImageDimensions inDimensions,
                   Pixel::Format pixelFormat,
                   unsigned char * __restrict__ outPixels,
                   ImageDimensions outDimensions )
{
  // Check the pixel format is one that is supported:
  if( pixelFormat == Pixel::RGB888 || pixelFormat == Pixel::RGBA8888 || pixelFormat == Pixel::L8 || pixelFormat == Pixel::A8 || pixelFormat == Pixel::LA88 || pixelFormat == Pixel::RGB565 )
  {
    if( pixelFormat == Pixel::RGB888 )
    {
      LinearSample3BPP( inPixels, inDimensions, outPixels, outDimensions );
    }
    else if( pixelFormat == Pixel::RGBA8888 )
    {
      LinearSample4BPP( inPixels, inDimensions, outPixels, outDimensions );
    }
    else if( pixelFormat == Pixel::L8 || pixelFormat == Pixel::A8 )
    {
      LinearSample1BPP( inPixels, inDimensions, outPixels, outDimensions );
    }
    else if( pixelFormat == Pixel::LA88 )
    {
      LinearSample2BPP( inPixels, inDimensions, outPixels, outDimensions );
    }
    else if ( pixelFormat == Pixel::RGB565 )
    {
      LinearSampleRGB565( inPixels, inDimensions, outPixels, outDimensions );
    }
    else
    {
      DALI_ASSERT_DEBUG( false == "Inner branch conditions don't match outer branch." );
    }
  }
  else
  {
    DALI_LOG_INFO( gImageOpsLogFilter, Dali::Integration::Log::Verbose, "Bitmap was not linear sampled: unsupported pixel format: %u.\n", unsigned(pixelFormat) );
  }
}

void RotateByShear( const uint8_t* const pixelsIn,
                    unsigned int widthIn,
                    unsigned int heightIn,
                    unsigned int pixelSize,
                    float radians,
                    uint8_t*& pixelsOut,
                    unsigned int& widthOut,
                    unsigned int& heightOut )
{
  // @note Code got from https://www.codeproject.com/Articles/202/High-quality-image-rotation-rotate-by-shear by Eran Yariv.

  // Do first the fast rotations to transform the angle into a (-45..45] range.

  float fastRotationPerformed = false;
  if( ( radians > Math::PI_4 ) && ( radians <= RAD_135 ) )
  {
    // Angle in (45.0 .. 135.0]
    // Rotate image by 90 degrees into temporary image,
    // so it requires only an extra rotation angle
    // of -45.0 .. +45.0 to complete rotation.
    Rotate90( pixelsIn,
              widthIn,
              heightIn,
              pixelSize,
              pixelsOut,
              widthOut,
              heightOut );
    radians -= Math::PI_2;
    fastRotationPerformed = true;
  }
  else if( ( radians > RAD_135 ) && ( radians <= RAD_225 ) )
  {
    // Angle in (135.0 .. 225.0]
    // Rotate image by 180 degrees into temporary image,
    // so it requires only an extra rotation angle
    // of -45.0 .. +45.0 to complete rotation.

    Rotate180( pixelsIn,
               widthIn,
               heightIn,
               pixelSize,
               pixelsOut );
    radians -= Math::PI;
    widthOut = widthIn;
    heightOut = heightIn;
    fastRotationPerformed = true;
  }
  else if( ( radians > RAD_225 ) && ( radians <= RAD_315 ) )
  {
    // Angle in (225.0 .. 315.0]
    // Rotate image by 270 degrees into temporary image,
    // so it requires only an extra rotation angle
    // of -45.0 .. +45.0 to complete rotation.

    Rotate270( pixelsIn,
               widthIn,
               heightIn,
               pixelSize,
               pixelsOut,
               widthOut,
               heightOut );
    radians -= RAD_270;
    fastRotationPerformed = true;
  }

  if( fabs( radians ) < Dali::Math::MACHINE_EPSILON_10 )
  {
    // Nothing else to do if the angle is zero.
    // The rotation angle was 90, 180 or 270.

    // @note Allocated memory by 'Fast Rotations', if any, has to be freed by the called to this function.
    return;
  }

  const uint8_t* const firstHorizontalSkwePixelsIn = fastRotationPerformed ? pixelsOut : pixelsIn;
  uint8_t*  tmpFirstHorizontalSkwePixelsIn = fastRotationPerformed ? pixelsOut : nullptr; // keep the pointer to free the memory.

  // Reset the input/output
  widthIn = widthOut;
  heightIn = heightOut;
  pixelsOut = nullptr;

  const float angleSinus = sin( radians );
  const float angleCosinus = cos( radians );
  const float angleTangent = tan( 0.5f * radians );

  ///////////////////////////////////////
  // Perform 1st shear (horizontal)
  ///////////////////////////////////////

  // Calculate first shear (horizontal) destination image dimensions

  widthOut = widthIn + static_cast<unsigned int>( fabs( angleTangent ) * static_cast<float>( heightIn ) );
  heightOut = heightIn;

  // Allocate the buffer for the 1st shear
  pixelsOut = static_cast<uint8_t*>( malloc( widthOut * heightOut * pixelSize ) );

  for( unsigned int y = 0u; y < heightOut; ++y )
  {
    const float shear = angleTangent * ( ( angleTangent >= 0.f ) ? ( 0.5f + static_cast<float>( y ) ) : ( 0.5f + static_cast<float>( y ) - static_cast<float>( heightOut ) ) );

    const int intShear = static_cast<int>( floor( shear ) );
    HorizontalSkew( firstHorizontalSkwePixelsIn, widthIn, pixelSize, pixelsOut, widthOut, y, intShear, shear - static_cast<float>( intShear ) );
  }

  // Free the memory allocated by the 'Fast Rotations'.
  free( tmpFirstHorizontalSkwePixelsIn );

  uint8_t* tmpPixelsIn = pixelsOut;
  unsigned int tmpWidthIn = widthOut;
  unsigned int tmpHeightIn = heightOut;

  // Reset the input/output
  pixelsOut = nullptr;

  ///////////////////////////////////////
  // Perform 2nd shear (vertical)
  ///////////////////////////////////////

  // Calc 2nd shear (vertical) destination image dimensions
  heightOut = static_cast<unsigned int>( static_cast<float>( widthIn ) * fabs( angleSinus ) + static_cast<float>( heightIn ) * angleCosinus );

  // Allocate the buffer for the 2nd shear
  pixelsOut = static_cast<uint8_t*>( malloc( widthOut * heightOut * pixelSize ) );

  // Variable skew offset
  float offset = angleSinus * ( ( angleSinus > 0.f ) ? static_cast<float>( widthIn - 1u ) : -( static_cast<float>( widthIn ) - static_cast<float>( widthOut ) ) );

  unsigned int column = 0u;
  for( column = 0u; column < widthOut; ++column, offset -= angleSinus )
  {
    const int shear = static_cast<int>( floor( offset ) );
    VerticalSkew( tmpPixelsIn, tmpWidthIn, tmpHeightIn, pixelSize, pixelsOut, widthOut, heightOut, column, shear, offset - static_cast<float>( shear ) );
  }

  // Free the memory allocated by the 'First Horizontal Skew'.
  free( tmpPixelsIn );

  // Reset the input/output
  tmpPixelsIn = pixelsOut;
  tmpWidthIn = widthOut;
  tmpHeightIn = heightOut;
  pixelsOut = nullptr;

  ///////////////////////////////////////
  // Perform 3rd shear (horizontal)
  ///////////////////////////////////////

  // Calc 3rd shear (horizontal) destination image dimensions
  widthOut = static_cast<unsigned int>( static_cast<float>( heightIn ) * fabs( angleSinus ) + static_cast<float>( widthIn ) * angleCosinus ) + 1u;

  // Allocate the buffer for the 3rd shear
  pixelsOut = static_cast<uint8_t*>( malloc( widthOut * heightOut * pixelSize ) );

  offset =  ( angleSinus >= 0.f ) ? -angleSinus * angleTangent * static_cast<float>( widthIn - 1u ) : angleTangent * ( static_cast<float>( widthIn - 1u ) * -angleSinus + ( 1.f - static_cast<float>( heightOut ) ) );

  for( unsigned int y = 0u; y < heightOut; ++y, offset += angleTangent )
  {
    const int shear = static_cast<int>( floor( offset ) );
    HorizontalSkew( tmpPixelsIn, tmpWidthIn, pixelSize, pixelsOut, widthOut, y, shear, offset - static_cast<float>( shear ) );
  }

  // Free the memory allocated by the 'First Horizontal Skew'.
  free( tmpPixelsIn );

  // @note Allocated memory by the last 'Horizontal Skew' has to be freed by the called to this function.
}

} /* namespace Platform */
} /* namespace Internal */
} /* namespace Dali */