FrameShrinkerAlpha.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_CV_FRAME_SHRINKER_ALPHA_H
#define META_OCEAN_CV_FRAME_SHRINKER_ALPHA_H
 
#include "ocean/cv/CV.h"
#include "ocean/cv/FrameBlender.h"
 
#include "ocean/base/Frame.h"
#include "ocean/base/Messenger.h"
#include "ocean/base/Worker.h"
 
namespace Ocean
{
 
namespace CV
{
 
/**
 * This class implements functions downsizing frames that hold alpha channels.
 * @ingroup cv
 */
class FrameShrinkerAlpha
{
    public:
 
        /**
         * The following comfort class provides comfortable functions simplifying prototyping applications but also increasing binary size of the resulting applications.
         * Best practice is to avoid using these functions if binary size matters,<br>
         * as for every comfort function a corresponding function exists with specialized functionality not increasing binary size significantly.<br>
         */
        class OCEAN_CV_EXPORT Comfort
        {
            public:
 
                /**
                 * Divides a given frame by two, taking four pixel values into account:<br>
                 * | 1 1 |<br>
                 * | 1 1 |<br>
                 * If the given source image has an odd frame dimension the last pixel row or the last pixel column is filtered together with the two valid rows or columns respectively.<br>
                 * If the type of the target frame does not match to the input frame the target frame (and image buffer) will be replaced by a correct one.
                 * @param source The source frame to resize
                 * @param target The target frame receiving the smaller frame data
                 * @param worker Optional worker object to distribute the computational load to several CPU cores
                 * @return True, if succeeded
                 */
                template <bool tTransparentIs0xFF>
                static bool divideByTwo(const Frame& source, Frame& target, Worker* worker = nullptr);
 
                /**
                 * Divides a given frame by two, taking four pixel values into account:<br>
                 * If the given source image has an odd frame dimension the last pixel row or the last pixel column is filtered together with the two valid rows or columns respectively.<br>
                 * @param frame The frame to resize
                 * @param worker Optional worker object to distribute the computational load to several CPU cores
                 * @return True, if succeeded
                 */
                template <bool tTransparentIs0xFF>
                static bool divideByTwo(Frame& frame, Worker* worker = nullptr);
        };
 
    public:
 
        /**
         * Divides a given 8 bit per channel frame by two, taking four pixel values into account:<br>
         * | 1 1 |<br>
         * | 1 1 |<br>
         * If the given source image has an odd frame dimension the last pixel row or the last pixel column is filtered together with the two valid rows or columns respectively.<br>
         * @param source The source frame buffer to resize
         * @param target The target frame buffer
         * @param sourceWidth Width of the source frame in pixel, with range [2, infinity)
         * @param sourceHeight Height of the source frame in pixel, with range [2, infinity)
         * @param sourcePaddingElements The number of padding elements at the end of each source row, in elements, with range [0, infinity)
         * @param targetPaddingElements The number of padding elements at the end of each target row, in elements, with range [0, infinity)
         * @param worker Optional worker object to distribute the computational load to several CPU cores
         * @tparam tChannels Number of channels of the frame (including the alpha channel), with range [1, infinity)
         * @tparam tAlphaAtFront True, if the alpha channel is in the front of the data channels
         * @tparam tTransparentIs0xFF True, if 0xFF is interpreted as fully transparent
         */
        template <unsigned int tChannels, bool tAlphaAtFront, bool tTransparentIs0xFF>
        static void divideByTwo8BitPerChannel(const uint8_t* source, uint8_t* target, const unsigned int sourceWidth, const unsigned int sourceHeight, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, Worker* worker = nullptr);
 
    private:
 
        /**
         * Divides a subset of a given 8 bit per channel frame by two, taking the average of four pixel values.
         * If the given source image has an odd frame dimension the last pixel row or the last pixel column is filtered together with the two valid rows or columns respectively.<br>
         * @param source The source frame buffer to resize
         * @param target The target frame buffer
         * @param sourceWidth Width of the source frame in pixel, with range [2, infinity)
         * @param sourceHeight Height of the source frame in pixel, with range [2, infinity)
         * @param sourcePaddingElements The number of padding elements at the end of each source row, in elements, with range [0, infinity)
         * @param targetPaddingElements The number of padding elements at the end of each target row, in elements, with range [0, infinity)
         * @param firstTargetRow First (including) row to halve
         * @param numberTargetRows Number of rows to halve
         * @tparam tChannels Number of channels of the frame (including the alpha channel), with range [1, infinity)
         * @tparam tAlphaAtFront True, if the alpha channel is in the front of the data channels
         * @tparam tTransparentIs0xFF True, if 0xFF is interpreted as fully transparent
         */
        template <unsigned int tChannels, bool tAlphaAtFront, bool tTransparentIs0xFF>
        static void divideByTwo8BitPerChannelSubset(const uint8_t* source, uint8_t* target, const unsigned int sourceWidth, const unsigned int sourceHeight, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int firstTargetRow, const unsigned int numberTargetRows);
};
 
template <unsigned int tChannels, bool tAlphaAtFront, bool tTransparentIs0xFF>
void FrameShrinkerAlpha::divideByTwo8BitPerChannel(const uint8_t* source, uint8_t* target, const unsigned int sourceWidth, const unsigned int sourceHeight, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, Worker* worker)
{
    static_assert(tChannels >= 1u, "Invalid channel number!");
 
    ocean_assert(source != nullptr && target != nullptr);
    ocean_assert(sourceWidth >= 2u && sourceHeight >= 2u);
 
    const unsigned int targetHeight = sourceHeight / 2u;
    ocean_assert(targetHeight > 0u);
 
    if (worker)
    {
        worker->executeFunction(Worker::Function::createStatic(&divideByTwo8BitPerChannelSubset<tChannels, tAlphaAtFront, tTransparentIs0xFF>, source, target, sourceWidth, sourceHeight, sourcePaddingElements, targetPaddingElements, 0u, 0u), 0u, targetHeight, 6u, 7u, 20u);
    }
    else
    {
        divideByTwo8BitPerChannelSubset<tChannels, tAlphaAtFront, tTransparentIs0xFF>(source, target, sourceWidth, sourceHeight, sourcePaddingElements, targetPaddingElements, 0u, targetHeight);
    }
}
 
template <unsigned int tChannels, bool tAlphaAtFront, bool tTransparentIs0xFF>
void FrameShrinkerAlpha::divideByTwo8BitPerChannelSubset(const uint8_t* source, uint8_t* target, const unsigned int sourceWidth, const unsigned int sourceHeight, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int firstTargetRow, const unsigned int numberTargetRows)
{
    static_assert(tChannels >= 1u, "Invalid channel number!");
 
    ocean_assert(source != nullptr && target != nullptr);
    ocean_assert(sourceWidth >= 2u && sourceHeight >= 2u);
    ocean_assert(firstTargetRow + numberTargetRows <= sourceHeight / 2u);
 
    const unsigned int targetWidth = sourceWidth / 2u;
 
    const unsigned int sourceStrideElements = sourceWidth * tChannels + sourcePaddingElements;
    const unsigned int targetStrideElements = targetWidth * tChannels + targetPaddingElements;
 
    const bool xEven = sourceWidth % 2u == 0u;
    const bool yEven = sourceHeight % 2u == 0u;
 
    const uint8_t* sourceFirst = source + firstTargetRow * 2u * sourceStrideElements;
    const uint8_t* sourceSecond = sourceFirst + sourceStrideElements;
 
    target += firstTargetRow * targetStrideElements;
 
    const bool threeBottomRows = !yEven && firstTargetRow + numberTargetRows == sourceHeight / 2u;
 
    const unsigned int numberTwoTargetRows = threeBottomRows ? (unsigned int)(max(int(numberTargetRows) - 1, 0)) : numberTargetRows;
    const unsigned int numberTwoTargetColumns = xEven ? targetWidth : (unsigned int)(max(int(targetWidth) - 1, 0));
 
    for (unsigned int y = 0u; y < numberTwoTargetRows; ++y)
    {
        for (unsigned int x = 0u; x < numberTwoTargetColumns; ++x)
        {
            // source0: | 1 1 |
            // source1: | 1 1 | / 4
 
            const unsigned int denominator = FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]);
 
            if (denominator != 0u)
            {
                const unsigned int denominator_2 = denominator / 2u;
 
                // data channel
                for (unsigned int n = FrameBlender::SourceOffset<tAlphaAtFront>::data(); n < tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::data() - 1u; ++n)
                    target[n] = uint8_t((sourceFirst[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceFirst[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels])
                                    + sourceSecond[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceSecond[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) + denominator_2) / denominator);
 
                // alpha channel
                target[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] = uint8_t((sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceFirst[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceSecond[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] + 2u) / 4u);
            }
            else
            {
                for (unsigned int n = 0u; n < tChannels; ++n)
                {
                    target[n] = uint8_t((sourceFirst[n] + sourceFirst[tChannels + n] + sourceSecond[n] + sourceSecond[tChannels + n] + 2u) / 4u);
                }
            }
 
            target += tChannels;
            sourceFirst += tChannels * 2u;
            sourceSecond += tChannels * 2u;
        }
 
        if (!xEven)
        {
            // three pixels left
 
            // source0: | 1 2 1 |
            // source1: | 1 2 1 | / 8
 
            const unsigned int denominator = FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]);
 
            if (denominator != 0u)
            {
                const unsigned int denominator_2 = denominator / 2u;
 
                // data channel
                for (unsigned int n = FrameBlender::SourceOffset<tAlphaAtFront>::data(); n < tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::data() - 1u; ++n)
                    target[n] = uint8_t((sourceFirst[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceFirst[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                    + sourceFirst[tChannels * 2u + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u])
                                    + sourceSecond[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceSecond[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                    + sourceSecond[tChannels * 2u + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]) + denominator_2) / denominator);
 
                // alpha channel
                target[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] =
                                uint8_t((sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceFirst[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                    + sourceFirst[tChannels * 2u + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceSecond[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                    + sourceSecond[tChannels * 2u + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] + 4u) / 8u);
            }
            else
            {
                for (unsigned int n = 0u; n < tChannels; ++n)
                {
                    target[n] = uint8_t((sourceFirst[n] + sourceFirst[tChannels + n] * 2u + sourceFirst[tChannels * 2u + n]
                                    + sourceSecond[n] + sourceSecond[tChannels + n] * 2u + sourceSecond[tChannels * 2u + n] + 4u) / 8u);
                }
            }
 
            target += tChannels;
            sourceFirst += tChannels * 3u;
            sourceSecond += tChannels * 3u;
        }
 
        target += targetPaddingElements;
        sourceFirst += sourcePaddingElements + sourceStrideElements;
        sourceSecond += sourcePaddingElements + sourceStrideElements;
    }
 
    if (threeBottomRows)
    {
        const uint8_t* sourceThird = sourceSecond + sourceStrideElements;
 
        for (unsigned int x = 0u; x < numberTwoTargetColumns; ++x)
        {
            // source0: | 1 1 |
            // source1: | 2 2 | / 8
            // source2: | 1 1 |
 
            const unsigned int denominator = FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]);
 
            if (denominator != 0u)
            {
                const unsigned int denominator_2 = denominator / 2u;
 
                // data channel
                for (unsigned int n = FrameBlender::SourceOffset<tAlphaAtFront>::data(); n < tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::data() - 1u; ++n)
                    target[n] = uint8_t((sourceFirst[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceFirst[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels])
                                    + sourceSecond[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]) * 2u
                                    + sourceSecond[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                    + sourceThird[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceThird[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) + denominator_2) / denominator);
 
                // alpha channel
                target[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] =
                                uint8_t((sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceFirst[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                    + sourceSecond[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                    + sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                    + sourceThird[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] + 4u) / 8u);
            }
            else
            {
                for (unsigned int n = 0u; n < tChannels; ++n)
                {
                    target[n] = uint8_t((sourceFirst[n] + sourceFirst[tChannels + n]
                                    + sourceSecond[n] * 2u + sourceSecond[tChannels + n] * 2u
                                    + sourceThird[n] + sourceThird[tChannels + n] + 4u) / 8u);
                }
            }
 
            target += tChannels;
            sourceFirst += tChannels * 2u;
            sourceSecond += tChannels * 2u;
            sourceThird += tChannels * 2u;
        }
 
        if (!xEven)
        {
            // three pixels left
 
            // source0: | 1 2 1 |
            // source1: | 2 4 2 | / 16
            // source2: | 1 2 1 |
 
 
            const unsigned int denominator = FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 4u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                                + FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]);
 
            if (denominator != 0u)
            {
                const unsigned int denominator_2 = denominator / 2u;
 
                // data channel
                for (unsigned int n = FrameBlender::SourceOffset<tAlphaAtFront>::data(); n < tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::data() - 1u; ++n)
                    target[n] = uint8_t((sourceFirst[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceFirst[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                    + sourceFirst[tChannels * 2u + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u])
                                    + sourceSecond[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]) * 2u
                                    + sourceSecond[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 4u
                                    + sourceSecond[tChannels * 2u + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]) * 2u
                                    + sourceThird[n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()])
                                    + sourceThird[tChannels + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels]) * 2u
                                    + sourceThird[tChannels * 2u + n] * FrameBlender::alpha8BitToOpaqueIs0xFF<tTransparentIs0xFF>(sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>() + tChannels * 2u]) + denominator_2) / denominator);
 
                // alpha channel
                target[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] =
                                uint8_t((sourceFirst[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceFirst[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                + sourceFirst[tChannels * 2u + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceSecond[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                + sourceSecond[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 4u
                                + sourceSecond[tChannels * 2u + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                + sourceThird[FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()]
                                + sourceThird[tChannels + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] * 2u
                                + sourceThird[tChannels * 2u + FrameBlender::SourceOffset<tAlphaAtFront>::template alpha<tChannels>()] + 8u) / 16u);
            }
            else
            {
                for (unsigned int n = 0u; n < tChannels; ++n)
                    target[n] = uint8_t((sourceFirst[n] + sourceFirst[tChannels + n] * 2u + sourceFirst[tChannels * 2u + n]
                                    + sourceSecond[n] * 2u + sourceSecond[tChannels + n] * 4u + sourceSecond[tChannels * 2u + n] * 2u
                                    + sourceThird[n] + sourceThird[tChannels + n] * 2u + sourceThird[tChannels * 2u + n] + 4u) / 8u);
            }
        }
    }
}
 
}
 
}
 
#endif // META_OCEAN_CV_FRAME_SHRINKER_ALPHA_H