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#include "opencv2/opencv.hpp"

using namespace cv;

void opencv_simple_median(IplImage *_src, IplImage *_dst)
{
    Mat src(_src);
    Mat dst(_dst);
    Vec2b buffer[3];
    int row, col, i;

    for (row = 0; row < src.rows; row++) {
        for (col = 0; col < src.cols; col++) {
            Vec2b p;
            p = src.at<Vec2b>(row, col);

            Vec2b t[3];
            t[2] = buffer[2] = buffer[1];
            t[1] = buffer[1] = buffer[0];
            t[0] = buffer[0] = p;

            // Because we have a buffer above, the start of one line
            // will be processed with data from the previous line.
            // The check below is a simple, relatively unsophisticated
            // way to handle the edge condition.  It does result in
            // introducing a spatial shift in the image because the
            // filter is non-causal.
            if (col > 1) {
                for (i = 0; i < 2; i++) {
                    bool a = t[2].val[i] > t[1].val[i];
                    bool b = t[2].val[i] > t[0].val[i];
                    bool c = t[1].val[i] > t[0].val[i];

                    if (a && c)
                        p.val[i] = t[1].val[i];
                    else if (b && !c)
                        p.val[i] = t[0].val[i];
                    else
                        p.val[i] = t[2].val[i];
                }
            }

            dst.at<Vec2b>(row, col) = p;
        }
    }
}
