Function compute_resize_area_tab

dnn/src/x86/resize/resize_cv.cpp:1909–1945

}

int compute_resize_area_tab(
        int ssize, int dsize, int cn, double scale, DecimateAlpha* tab) {
    int k = 0;
    for (int dx = 0; dx < dsize; dx++) {
        double fsx1 = dx * scale;
        double fsx2 = fsx1 + scale;
        double cellWidth = std::min(scale, ssize - fsx1);

        int sx1 = ceil(fsx1), sx2 = floor(fsx2);

        sx2 = std::min(sx2, ssize - 1);
        sx1 = std::min(sx1, sx2);

        if (sx1 - fsx1 > 1e-3) {
            megdnn_assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = (sx1 - 1) * cn;
            tab[k++].alpha = (float)((sx1 - fsx1) / cellWidth);
        }

        for (int sx = sx1; sx < sx2; sx++) {
            megdnn_assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = sx * cn;
            tab[k++].alpha = float(1.0 / cellWidth);
        }

        if (fsx2 - sx2 > 1e-3) {
            megdnn_assert(k < ssize * 2);
            tab[k].di = dx * cn;
            tab[k].si = sx2 * cn;
            tab[k++].alpha =
                    (float)(std::min(std::min(fsx2 - sx2, 1.), cellWidth) / cellWidth);
        }
    }
    return k;
}

// resize Area Fast
template <typename T, typename WT, typename VecOp>