Function nms_boxes

examples/mtcnn/mtcnn_utils.cpp:105–165

}

void nms_boxes(std::vector<face_box>& input, float threshold, int type, std::vector<face_box>& output)
{
    output.clear();
    std::sort(input.begin(), input.end(), [](const face_box& a, const face_box& b) { return a.score > b.score; });

    int box_num = input.size();

    std::vector<int> merged(box_num, 0);

    for(int i = 0; i < box_num; i++)
    {
        if(merged[i])
            continue;

        output.push_back(input[i]);

        float h0 = input[i].y1 - input[i].y0 + 1;
        float w0 = input[i].x1 - input[i].x0 + 1;

        float area0 = h0 * w0;

        for(int j = i + 1; j < box_num; j++)
        {
            if(merged[j])
                continue;

            float inner_x0 = std::max(input[i].x0, input[j].x0);
            float inner_y0 = std::max(input[i].y0, input[j].y0);

            float inner_x1 = std::min(input[i].x1, input[j].x1);
            float inner_y1 = std::min(input[i].y1, input[j].y1);

            float inner_h = inner_y1 - inner_y0 + 1;
            float inner_w = inner_x1 - inner_x0 + 1;

            if(inner_h <= 0 || inner_w <= 0)
                continue;

            float inner_area = inner_h * inner_w;

            float h1 = input[j].y1 - input[j].y0 + 1;
            float w1 = input[j].x1 - input[j].x0 + 1;

            float area1 = h1 * w1;

            float score;

            if(type == NMS_UNION)
            {
                score = inner_area / (area0 + area1 - inner_area);
            }
            else
            {
                score = inner_area / std::min(area0, area1);
            }

            if(score > threshold)
                merged[j] = 1;