Function getStructuringElement

tools/cv/source/imgproc/filter.cpp:381–411

VARP getStructuringElement(int shape, Size ksize) {
    // shape: MORPH_RECT = 0, MORPH_CROSS = 1, MORPH_ELLIPSE = 2
    std::vector<uint8_t> elem(ksize.area());
    int anchor_x = ksize.width / 2, anchor_y = ksize.height / 2, r, c;
    double inv_r2 = 0;
    if(shape == 2) {
        r = anchor_y;
        c = anchor_x;
        inv_r2 = r ? 1. / ((double)r * r) : 0;
    }
    for(int i = 0; i < ksize.height; i++ ) {
        uint8_t* ptr = elem.data() + i * ksize.width;
        int start_x = 0, end_x = 0;
        if(shape == 0 || (shape == 1 && i == anchor_y)) {
            end_x = ksize.width;
        } else if(shape == 1) {
            start_x = anchor_x, end_x = start_x + 1;
        } else {
            int dy = i - r;
            if (std::abs(dy) <= r) {
                int dx = static_cast<int>(c * std::sqrt((r*r - dy*dy)*inv_r2));
                start_x = std::max(c - dx, 0);
                end_x = std::min(c + dx + 1, ksize.width);
            }
        }
        for(int j = 0; j < ksize.width; j++) {
            ptr[j] = (j >= start_x && j < end_x);
        }
    }
    return _Const(elem.data(), { ksize.height, ksize.width }, NHWC, halide_type_of<uint8_t>());
}

VARP GaussianBlur(VARP src, Size ksize, double sigmaX, double sigmaY, int borderType) {
    auto kernelX = getGaussianKernel(ksize.width, sigmaX);