    // Copyright (C) 2011  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_DETECTION_TEMPlATE_TOOLS_H__
    #define DLIB_DETECTION_TEMPlATE_TOOLS_H__

    #include "detection_template_tools_abstract.h"
    #include "../geometry.h"
    #include "../matrix.h"
    #include <utility>
    #include <vector>
    #include <cmath>

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        inline rectangle compute_box_dimensions (
            const double width_to_height_ratio,
            const double area
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(width_to_height_ratio > 0 && area > 0,
                "\t rectangle compute_box_dimensions()"
                << "\n\t Invalid arguments were given to this function. "
                << "\n\t width_to_height_ratio: " << width_to_height_ratio
                << "\n\t area: " << area
                );

            /*
                width*height == area
                width/height == width_to_height_ratio
            */
            using namespace std;

            const int height = (int)std::floor(std::sqrt(area/width_to_height_ratio) + 0.5);
            const int width  = (int)std::floor(area/height + 0.5);

            return centered_rect(0,0,width,height);
        }

    // ----------------------------------------------------------------------------------------

        inline std::vector<rectangle> create_single_box_detection_template (
            const rectangle& object_box
        )
        {
            std::vector<rectangle> temp;
            temp.push_back(object_box);
            return temp;
        }

    // ----------------------------------------------------------------------------------------

        inline std::vector<rectangle> create_overlapped_2x2_detection_template (
            const rectangle& object_box
        )
        {
            std::vector<rectangle> result;

            const point c = center(object_box);

            result.push_back(rectangle() + c + object_box.tl_corner() + object_box.tr_corner());
            result.push_back(rectangle() + c + object_box.bl_corner() + object_box.br_corner());
            result.push_back(rectangle() + c + object_box.tl_corner() + object_box.bl_corner());
            result.push_back(rectangle() + c + object_box.tr_corner() + object_box.br_corner());

            return result;
        }

    // ----------------------------------------------------------------------------------------

        inline std::vector<rectangle> create_grid_detection_template (
            const rectangle& object_box,
            unsigned int cells_x,
            unsigned int cells_y
        )
        {
            // make sure requires clause is not broken
            DLIB_ASSERT(cells_x > 0 && cells_y > 0,
                "\t std::vector<rectangle> create_grid_detection_template()"
                << "\n\t The number of cells along a dimension can't be zero. "
                << "\n\t cells_x: " << cells_x
                << "\n\t cells_y: " << cells_y
                );

            std::vector<rectangle> result;

            const matrix<double,1> x = linspace(object_box.left(), object_box.right(), cells_x+1);
            const matrix<double,1> y = linspace(object_box.top(), object_box.bottom(), cells_y+1);

            for (long j = 0; j+1 < y.size(); ++j)
            {
                for (long i = 0; i+1 < x.size(); ++i)
                {
                    const dlib::vector<double,2> tl(x(i),y(j));
                    const dlib::vector<double,2> br(x(i+1),y(j+1));
                    result.push_back(rectangle(tl,br));
                }
            }

            return result;
        }

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_DETECTION_TEMPlATE_TOOLS_H__