FrameFilterMin.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_FILTER_MIN_H
#define META_OCEAN_CV_FRAME_FILTER_MIN_H
 
#include "ocean/cv/CV.h"
#include "ocean/cv/FrameFilterSorted.h"
 
#include "ocean/base/Frame.h"
#include "ocean/base/Worker.h"
 
#include "ocean/math/Numeric.h"
 
namespace Ocean
{
 
namespace CV
{
 
/**
 * This class implements filters based on the min function.
 * @ingroup cv
 */
class OCEAN_CV_EXPORT FrameFilterMin : protected FrameFilterSorted
{
    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:
 
                /**
                 * Filters a frame with a min filter with arbitrary size (a square patch).
                 * @param source The source image to be filtered, must be valid
                 * @param target The target frame with same size and pixel format receiving the filtered result, must be valid
                 * @param filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
                 * @param worker Optional worker object to distribute the computation
                 * @return True, if succeeded
                 */
                static bool filter(const Frame& source, Frame& target, const unsigned int filterSize, Worker* worker);
 
                /**
                 * Filters a frame with a min filter with arbitrary size (a square patch).
                 * @param frame The image to be filtered, must be valid
                 * @param filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
                 * @param worker Optional worker object to distribute the computation
                 * @return True, if succeeded
                 */
                static bool filter(Frame& frame, const unsigned int filterSize, Worker* worker);
        };
 
    public:
 
        /**
         * Filters a frame with a min filter with arbitrary size (a square patch).
         * @param source The source image to be filtered, must be valid
         * @param target The target frame with same size and pixel format receiving the filtered result, must be valid
         * @param width The width of the input frame in pixel, with range [filterSize / 2, infinity)
         * @param height The height of the input frame in pixel, with range [filterSize / 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 filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
         * @param worker Optional worker object to distribute the computation
         * @tparam T Data type of the data elements
         * @tparam tChannels Number of data channels, with range [1, infinity)
         */
        template <typename T, unsigned int tChannels>
        static void filter(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, Worker* worker = nullptr);
 
        /**
         * Filters a frame with a min filter with arbitrary size (a square patch).
         * @param frame The image to be filtered, must be valid
         * @param width The width of the input frame in pixel, with range [filterSize / 2, infinity)
         * @param height The height of the input frame in pixel, with range [filterSize / 2, infinity)
         * @param framePaddingElements The number of padding elements at the end of each frame row, in elements, with range [0, infinity)
         * @param filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
         * @param worker Optional worker object to distribute the computation
         * @tparam T Data type of the data elements
         * @tparam tChannels Number of data channels, with range [1, infinity)
         */
        template <typename T, unsigned int tChannels>
        static void filter(T* frame, const unsigned int width, const unsigned int height, const unsigned int framePaddingElements, const unsigned int filterSize, Worker* worker = nullptr);
 
    protected:
 
        /**
         * Filters a subset of an integer frame with a min filter with arbitrary size.
         * @param source The source image to be filtered, must be valid
         * @param target The target frame with same size and pixel format receiving the filtered result, must be valid
         * @param width The width of the input frame in pixel, with range [filterSize / 2, infinity)
         * @param height The height of the input frame in pixel, with range [filterSize / 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 filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
         * @param firstRow First row to be handled, with range [0, height - 1]
         * @param numberRows Number of rows to be handled, with range [1, height - firstRow]
         * @tparam T Data type of the data elements, must be an integer data type
         * @tparam tChannels Number of data channels, with range [1, infinity)
         */
        template <typename T, unsigned int tChannels, typename THistogram>
        static void filterHistogramSubset(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, const unsigned int firstRow, const unsigned int numberRows);
 
        /**
         * Filters a subset of a floating point frame with a min filter with arbitrary size.
         * @param source The source image to be filtered, must be valid
         * @param target The target frame with same size and pixel format receiving the filtered result, must be valid
         * @param width The width of the input frame in pixel, with range [filterSize / 2, infinity)
         * @param height The height of the input frame in pixel, with range [filterSize / 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 filterSize Size of the filter edge in pixel, must be odd with range [1, infinity)
         * @param firstRow First row to be handled, with range [0, height - 1]
         * @param numberRows Number of rows to be handled, with range [1, height - firstRow]
         * @tparam T Data type of the data elements, must be a valid data type
         * @tparam tChannels Number of data channels, with range [1, infinity)
         */
        template <typename T, unsigned int tChannels>
        static void filterSequentialSubset(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, const unsigned int firstRow, const unsigned int numberRows);
};
 
template <typename T, unsigned int tChannels>
void FrameFilterMin::filter(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, Worker* worker)
{
    static_assert(tChannels != 0u, "Invalid channel number!");
 
    ocean_assert(source != nullptr && target != nullptr && source != target);
    ocean_assert(filterSize / 2u <= width && filterSize / 2u <= height);
 
    if constexpr (std::is_floating_point<T>::value || sizeof(T) > sizeof(uint16_t))
    {
        if (worker)
        {
            worker->executeFunction(Worker::Function::createStatic(&filterSequentialSubset<T, tChannels>, source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, 0u), 0u, height, 7u, 8u, 20u);
        }
        else
        {
            filterSequentialSubset<T, tChannels>(source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, height);
        }
    }
    else if (filterSize < 5u)
    {
        if (worker)
        {
            worker->executeFunction(Worker::Function::createStatic(&filterSequentialSubset<T, tChannels>, source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, 0u), 0u, height, 7u, 8u, 20u);
        }
        else
        {
            filterSequentialSubset<T, tChannels>(source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, height);
        }
    }
    else
    {
        ocean_assert(!std::is_floating_point<T>::value);
 
        ocean_assert(uint64_t(filterSize * filterSize) < uint64_t(NumericT<uint16_t>::maxValue()));
 
        constexpr size_t histogramElements = 1 << sizeof(T) * 8;
 
        ocean_assert(sizeof(T) != sizeof(uint8_t) || histogramElements == 256);
        ocean_assert(sizeof(T) != sizeof(uint16_t) || histogramElements == 65536);
 
        typedef HistogramInteger<T, uint16_t, histogramElements> Histogram;
 
        if (worker)
        {
            worker->executeFunction(Worker::Function::createStatic(&filterHistogramSubset<T, tChannels, Histogram>, source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, 0u), 0u, height, 7u, 8u, 20u);
        }
        else
        {
            filterHistogramSubset<T, tChannels, Histogram>(source, target, width, height, sourcePaddingElements, targetPaddingElements, filterSize, 0u, height);
        }
    }
}
 
template <typename T, unsigned int tChannels>
void FrameFilterMin::filter(T* frame, const unsigned int width, const unsigned int height, const unsigned int framePaddingElements, const unsigned int filterSize, Worker* worker)
{
    static_assert(tChannels != 0u, "Invalid channel number!");
 
    ocean_assert(frame != nullptr);
    ocean_assert(filterSize / 2u <= width && filterSize / 2u <= height);
 
    Memory memory(width * height * sizeof(T) * tChannels);
 
    constexpr unsigned int memoryPaddingElements = 0u;
    filter<T, tChannels>(frame, memory.data<T>(), width, height, framePaddingElements, memoryPaddingElements, filterSize, worker);
 
    if (framePaddingElements == 0u)
    {
        memcpy(frame, memory.data(), memory.size());
    }
    else
    {
        const T* memoryData = memory.data<T>();
 
        for (unsigned int y = 0u; y < height; ++y)
        {
            memcpy(frame, memoryData, width * tChannels * sizeof(T));
 
            frame += width * tChannels + framePaddingElements;
            memoryData += width * tChannels + memoryPaddingElements;
        }
    }
}
 
template <typename T, unsigned int tChannels, typename THistogram>
void FrameFilterMin::filterHistogramSubset(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, const unsigned int firstRow, const unsigned int numberRows)
{
    static_assert(!std::is_floating_point<T>::value, "Invalid data type!");
    static_assert(tChannels != 0u, "Invalid channel number");
 
    ocean_assert(source != nullptr && target != nullptr);
 
    ocean_assert(filterSize >= 3u && filterSize % 2u == 1u);
 
    const unsigned int filterSize_2 = filterSize / 2u;
    ocean_assert(filterSize_2 <= width && filterSize_2 <= height);
 
    const unsigned int endRow = firstRow + numberRows;
 
    const unsigned int sourceStrideElements = width * tChannels + sourcePaddingElements;
    const unsigned int targetStrideElements = width * tChannels + targetPaddingElements;
 
    THistogram histogram[tChannels];
 
    // fill initial histogram
 
    for (unsigned int y = clampLower(firstRow, filterSize_2); y <= clampUpper(firstRow, filterSize_2, height); ++y)
    {
        const T* sourceRow = source + y * sourceStrideElements;
 
        for (unsigned int x = 0u; x <= filterSize_2; ++x)
        {
            for (unsigned int n = 0u; n < tChannels; ++n)
            {
                histogram[n].pushValue(*sourceRow++);
            }
        }
    }
 
    ocean_assert(histogram[0].values() >= (filterSize_2 + 1u) * (filterSize_2 + 1u));
    ocean_assert(histogram[0].values() <= (filterSize_2 + 1u) * filterSize);
 
    THistogram previousHistograms[tChannels];
 
    for (unsigned int y = firstRow; y < endRow; ++y)
    {
        T* targetRow = target + y * targetStrideElements;
 
        // making a copy which we can use when we start with the next row
        for (unsigned int n = 0u; n < tChannels; ++n)
        {
            previousHistograms[n] = histogram[n];
        }
 
        for (unsigned int x = 0u; x < width; ++x)
        {
            for (unsigned int n = 0u; n < tChannels; ++n)
            {
                ocean_assert(histogram[n]);
                *targetRow++ = histogram[n].minValue();
            }
 
            if (x != width - 1u)
            {
                ocean_assert(x + 1u < width);
 
                // horizontal histogram update
 
                for (unsigned int yy = clampLower(y, filterSize_2); yy <= clampUpper(y, filterSize_2, height); ++yy)
                {
                    const T* sourceRow = source + yy * sourceStrideElements;
 
                    const unsigned int xxLeft = x - filterSize_2;
                    const unsigned int xxRight = x + filterSize_2 + 1u;
 
                    if (xxLeft < width) // handling negative cases: int(xxLeft) < 0
                    {
                        for (unsigned int n = 0u; n < tChannels; ++n)
                        {
                            const T popValue = sourceRow[xxLeft * tChannels + n];
 
                            ocean_assert(histogram[n].hasValue(popValue));
                            histogram[n].popValue(popValue);
                        }
                    }
 
                    if (xxRight < width)
                    {
                        for (unsigned int n = 0u; n < tChannels; ++n)
                        {
                            const T pushValue = sourceRow[xxRight * tChannels + n];
 
                            histogram[n].pushValue(pushValue);
                        }
                    }
                }
            }
 
            ocean_assert(histogram[0].values() <= filterSize * filterSize);
        }
 
        if (y != endRow - 1u)
        {
            ocean_assert(y + 1u < endRow);
 
            // vertical histogram update at the beginning of the row
 
            for (unsigned int n = 0u; n < tChannels; ++n)
            {
                histogram[n] = previousHistograms[n];
            }
 
            const unsigned int yyTop = y - filterSize_2;
            const unsigned int yyBottom = y + filterSize_2 + 1u;
 
            if (yyTop < height) // handling negative cases: int(yyTop) < 0
            {
                const T* sourceRow = source + yyTop * sourceStrideElements;
 
                for (unsigned int x = 0u; x <= filterSize_2; ++x)
                {
                    for (unsigned int n = 0u; n < tChannels; ++n)
                    {
                        const T popValue = sourceRow[x * tChannels + n];
 
                        ocean_assert(histogram[n].hasValue(popValue));
                        histogram[n].popValue(popValue);
                    }
                }
            }
 
            if (yyBottom < height)
            {
                const T* sourceRow = source + yyBottom * sourceStrideElements;
 
                for (unsigned int x = 0u; x <= filterSize_2; ++x)
                {
                    for (unsigned int n = 0u; n < tChannels; ++n)
                    {
                        const T pushValue = sourceRow[x * tChannels + n];
 
                        histogram[n].pushValue(pushValue);
                    }
                }
            }
        }
    }
}
 
template <typename T, unsigned int tChannels>
void FrameFilterMin::filterSequentialSubset(const T* source, T* target, const unsigned int width, const unsigned int height, const unsigned int sourcePaddingElements, const unsigned int targetPaddingElements, const unsigned int filterSize, const unsigned int firstRow, const unsigned int numberRows)
{
    static_assert(tChannels != 0u, "Invalid channel number");
 
    ocean_assert(source != nullptr && target != nullptr);
    ocean_assert(firstRow + numberRows <= height);
 
    const unsigned int sourceStrideElements = width * tChannels + sourcePaddingElements;
    const unsigned int targetStrideElements = width * tChannels + targetPaddingElements;
 
    const unsigned int filterSize_2 = filterSize / 2u;
 
    T minValues[tChannels];
 
    for (unsigned int y = firstRow; y < firstRow + numberRows; ++y)
    {
        T* targetRow = target + y * targetStrideElements;
 
        for (unsigned int x = 0u; x < width; ++x)
        {
            for (unsigned int n = 0u; n < tChannels; ++n)
            {
                minValues[n] = NumericT<T>::maxValue();
            }
 
            for (unsigned int xx = max(0, int(x) - int(filterSize_2)); xx < min(x + filterSize_2 + 1u, width); ++xx)
            {
                for (unsigned int yy = max(0, int(y) - int(filterSize_2)); yy < min(y + filterSize_2 + 1u, height); ++yy)
                {
                    ocean_assert(xx < width && yy < height);
 
                    const T* const sourcePixel = source + yy * sourceStrideElements + xx * tChannels;
 
                    for (unsigned int n = 0u; n < tChannels; ++n)
                    {
                        if (sourcePixel[n] < minValues[n])
                        {
                            minValues[n] = sourcePixel[n];
                        }
                    }
                }
            }
 
            for (unsigned int n = 0u; n < tChannels; ++n)
            {
                targetRow[n] = minValues[n];
            }
 
            targetRow += tChannels;
        }
    }
}
 
}
 
}
 
#endif // META_OCEAN_CV_FRAME_FILTER_MIN_H