photo/src/fast_nlmeans_denoising_invoker.hpp

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#ifndef __OPENCV_FAST_NLMEANS_DENOISING_INVOKER_HPP__
#define __OPENCV_FAST_NLMEANS_DENOISING_INVOKER_HPP__

#include "precomp.hpp"
#include <limits>

#include "fast_nlmeans_denoising_invoker_commons.hpp"
#include "arrays.hpp"

using namespace cv;

template <typename T, typename IT, typename UIT, typename D, typename WT>
struct FastNlMeansDenoisingInvoker :
        public ParallelLoopBody
{
public:
    FastNlMeansDenoisingInvoker(const Mat& src, Mat& dst,
        int template_window_size, int search_window_size, const float *h);

    void operator() (const Range& range) const;

private:
    void operator= (const FastNlMeansDenoisingInvoker&);

    const Mat& src_;
    Mat& dst_;

    Mat extended_src_;
    int border_size_;

    int template_window_size_;
    int search_window_size_;

    int template_window_half_size_;
    int search_window_half_size_;

    typename pixelInfo<WT>::sampleType fixed_point_mult_;
    int almost_template_window_size_sq_bin_shift_;
    std::vector<WT> almost_dist2weight_;

    void calcDistSumsForFirstElementInRow(
        int i, Array2d<int>& dist_sums,
        Array3d<int>& col_dist_sums,
        Array3d<int>& up_col_dist_sums) const;

    void calcDistSumsForElementInFirstRow(
        int i, int j, int first_col_num,
        Array2d<int>& dist_sums,
        Array3d<int>& col_dist_sums,
        Array3d<int>& up_col_dist_sums) const;
};

inline int getNearestPowerOf2(int value)
{
    int p = 0;
    while( 1 << p < value)
        ++p;
    return p;
}

template <typename T, typename IT, typename UIT, typename D, typename WT>
FastNlMeansDenoisingInvoker<T, IT, UIT, D, WT>::FastNlMeansDenoisingInvoker(
    const Mat& src, Mat& dst,
    int template_window_size,
    int search_window_size,
    const float *h) :
    src_(src), dst_(dst)
{
    CV_Assert(src.channels() == pixelInfo<T>::channels);

    template_window_half_size_ = template_window_size / 2;
    search_window_half_size_   = search_window_size   / 2;
    template_window_size_      = template_window_half_size_ * 2 + 1;
    search_window_size_        = search_window_half_size_   * 2 + 1;

    border_size_ = search_window_half_size_ + template_window_half_size_;
    copyMakeBorder(src_, extended_src_, border_size_, border_size_, border_size_, border_size_, BORDER_DEFAULT);

    const IT max_estimate_sum_value =
        (IT)search_window_size_ * (IT)search_window_size_ * (IT)pixelInfo<T>::sampleMax();
    fixed_point_mult_ = (int)std::min<IT>(std::numeric_limits<IT>::max() / max_estimate_sum_value,
                                          pixelInfo<WT>::sampleMax());

    // precalc weight for every possible l2 dist between blocks
    // additional optimization of precalced weights to replace division(averaging) by binary shift
    CV_Assert(template_window_size_ <= 46340); // sqrt(INT_MAX)
    int template_window_size_sq = template_window_size_ * template_window_size_;
    almost_template_window_size_sq_bin_shift_ = getNearestPowerOf2(template_window_size_sq);
    double almost_dist2actual_dist_multiplier = ((double)(1 << almost_template_window_size_sq_bin_shift_)) / template_window_size_sq;

    int max_dist = D::template maxDist<T>();
    int almost_max_dist = (int)(max_dist / almost_dist2actual_dist_multiplier + 1);
    almost_dist2weight_.resize(almost_max_dist);

    for (int almost_dist = 0; almost_dist < almost_max_dist; almost_dist++)
    {
        double dist = almost_dist * almost_dist2actual_dist_multiplier;
        almost_dist2weight_[almost_dist] =
            D::template calcWeight<T, WT>(dist, h, fixed_point_mult_);
    }

    // additional optimization init end
    if (dst_.empty())
        dst_ = Mat::zeros(src_.size(), src_.type());
}

template <typename T, typename IT, typename UIT, typename D, typename WT>
void FastNlMeansDenoisingInvoker<T, IT, UIT, D, WT>::operator() (const Range& range) const
{
    int row_from = range.start;
    int row_to = range.end - 1;

    // sums of cols anf rows for current pixel p
    Array2d<int> dist_sums(search_window_size_, search_window_size_);

    // for lazy calc optimization (sum of cols for current pixel)
    Array3d<int> col_dist_sums(template_window_size_, search_window_size_, search_window_size_);

    int first_col_num = -1;
    // last elements of column sum (for each element in row)
    Array3d<int> up_col_dist_sums(src_.cols, search_window_size_, search_window_size_);

    for (int i = row_from; i <= row_to; i++)
    {
        for (int j = 0; j < src_.cols; j++)
        {
            int search_window_y = i - search_window_half_size_;
            int search_window_x = j - search_window_half_size_;

            // calc dist_sums
            if (j == 0)
            {
                calcDistSumsForFirstElementInRow(i, dist_sums, col_dist_sums, up_col_dist_sums);
                first_col_num = 0;
            }
            else
            {
                // calc cur dist_sums using previous dist_sums
                if (i == row_from)
                {
                    calcDistSumsForElementInFirstRow(i, j, first_col_num,
                        dist_sums, col_dist_sums, up_col_dist_sums);
                }
                else
                {
                    int ay = border_size_ + i;
                    int ax = border_size_ + j + template_window_half_size_;

                    int start_by = border_size_ + i - search_window_half_size_;
                    int start_bx = border_size_ + j - search_window_half_size_ + template_window_half_size_;

                    T a_up = extended_src_.at<T>(ay - template_window_half_size_ - 1, ax);
                    T a_down = extended_src_.at<T>(ay + template_window_half_size_, ax);

                    // copy class member to local variable for optimization
                    int search_window_size = search_window_size_;

                    for (int y = 0; y < search_window_size; y++)
                    {
                        int * dist_sums_row = dist_sums.row_ptr(y);
                        int * col_dist_sums_row = col_dist_sums.row_ptr(first_col_num, y);
                        int * up_col_dist_sums_row = up_col_dist_sums.row_ptr(j, y);

                        const T * b_up_ptr = extended_src_.ptr<T>(start_by - template_window_half_size_ - 1 + y);
                        const T * b_down_ptr = extended_src_.ptr<T>(start_by + template_window_half_size_ + y);

                        for (int x = 0; x < search_window_size; x++)
                        {
                            // remove from current pixel sum column sum with index "first_col_num"
                            dist_sums_row[x] -= col_dist_sums_row[x];

                            int bx = start_bx + x;
                            col_dist_sums_row[x] = up_col_dist_sums_row[x] + D::template calcUpDownDist<T>(a_up, a_down, b_up_ptr[bx], b_down_ptr[bx]);

                            dist_sums_row[x] += col_dist_sums_row[x];
                            up_col_dist_sums_row[x] = col_dist_sums_row[x];
                        }
                    }
                }

                first_col_num = (first_col_num + 1) % template_window_size_;
            }

            // calc weights
            IT estimation[pixelInfo<T>::channels], weights_sum[pixelInfo<WT>::channels];
            for (int channel_num = 0; channel_num < pixelInfo<T>::channels; channel_num++)
                estimation[channel_num] = 0;
            for (int channel_num = 0; channel_num < pixelInfo<WT>::channels; channel_num++)
                weights_sum[channel_num] = 0;

            for (int y = 0; y < search_window_size_; y++)
            {
                const T* cur_row_ptr = extended_src_.ptr<T>(border_size_ + search_window_y + y);
                int* dist_sums_row = dist_sums.row_ptr(y);
                for (int x = 0; x < search_window_size_; x++)
                {
                    int almostAvgDist = dist_sums_row[x] >> almost_template_window_size_sq_bin_shift_;
                    WT weight = almost_dist2weight_[almostAvgDist];
                    T p = cur_row_ptr[border_size_ + search_window_x + x];
                    incWithWeight<T, IT, WT>(estimation, weights_sum, weight, p);
                }
            }

            divByWeightsSum<IT, UIT, pixelInfo<T>::channels, pixelInfo<WT>::channels>(estimation,
                                                                                      weights_sum);
            dst_.at<T>(i,j) = saturateCastFromArray<T, IT>(estimation);
        }
    }
}

template <typename T, typename IT, typename UIT, typename D, typename WT>
inline void FastNlMeansDenoisingInvoker<T, IT, UIT, D, WT>::calcDistSumsForFirstElementInRow(
    int i,
    Array2d<int>& dist_sums,
    Array3d<int>& col_dist_sums,
    Array3d<int>& up_col_dist_sums) const
{
    int j = 0;

    for (int y = 0; y < search_window_size_; y++)
        for (int x = 0; x < search_window_size_; x++)
        {
            dist_sums[y][x] = 0;
            for (int tx = 0; tx < template_window_size_; tx++)
                col_dist_sums[tx][y][x] = 0;

            int start_y = i + y - search_window_half_size_;
            int start_x = j + x - search_window_half_size_;

            for (int ty = -template_window_half_size_; ty <= template_window_half_size_; ty++)
                for (int tx = -template_window_half_size_; tx <= template_window_half_size_; tx++)
                {
                    int dist = D::template calcDist<T>(extended_src_,
                        border_size_ + i + ty, border_size_ + j + tx,
                        border_size_ + start_y + ty, border_size_ + start_x + tx);

                    dist_sums[y][x] += dist;
                    col_dist_sums[tx + template_window_half_size_][y][x] += dist;
                }

            up_col_dist_sums[j][y][x] = col_dist_sums[template_window_size_ - 1][y][x];
        }
}

template <typename T, typename IT, typename UIT, typename D, typename WT>
inline void FastNlMeansDenoisingInvoker<T, IT, UIT, D, WT>::calcDistSumsForElementInFirstRow(
    int i, int j, int first_col_num,
    Array2d<int>& dist_sums,
    Array3d<int>& col_dist_sums,
    Array3d<int>& up_col_dist_sums) const
{
    int ay = border_size_ + i;
    int ax = border_size_ + j + template_window_half_size_;

    int start_by = border_size_ + i - search_window_half_size_;
    int start_bx = border_size_ + j - search_window_half_size_ + template_window_half_size_;

    int new_last_col_num = first_col_num;

    for (int y = 0; y < search_window_size_; y++)
        for (int x = 0; x < search_window_size_; x++)
        {
            dist_sums[y][x] -= col_dist_sums[first_col_num][y][x];

            col_dist_sums[new_last_col_num][y][x] = 0;
            int by = start_by + y;
            int bx = start_bx + x;
            for (int ty = -template_window_half_size_; ty <= template_window_half_size_; ty++)
                col_dist_sums[new_last_col_num][y][x] += D::template calcDist<T>(extended_src_, ay + ty, ax, by + ty, bx);

            dist_sums[y][x] += col_dist_sums[new_last_col_num][y][x];
            up_col_dist_sums[j][y][x] = col_dist_sums[new_last_col_num][y][x];
        }
}

#endif