    // Copyright (C) 2008  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_DRAW_IMAGe_
    #define DLIB_DRAW_IMAGe_

    #include "draw_abstract.h"
    #include "../algs.h"
    #include "../pixel.h"
    #include "../matrix.h"
    #include <cmath>

    namespace dlib
    {

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

        template <
            typename image_type,
            typename pixel_type
            >
        void draw_line (
            long x1,
            long y1,
            long x2,
            long y2,
            image_type& c_,
            const pixel_type& val
        )
        {
            image_view<image_type> c(c_);
            if (x1 == x2)
            {
                // make sure y1 comes before y2
                if (y1 > y2)
                    swap(y1,y2);

                if (x1 < 0 || x1 >= c.nc())
                    return;

                // this is a vertical line
                for (long y = y1; y <= y2; ++y)
                {
                    if (y < 0 || y >= c.nr())
                        continue;

                    assign_pixel(c[y][x1], val);
                }
            }
            else if (y1 == y2)
            {

                // make sure x1 comes before x2
                if (x1 > x2)
                    swap(x1,x2);

                if (y1 < 0 || y1 >= c.nr())
                    return;

                // this is a horizontal line
                for (long x = x1; x <= x2; ++x)
                {
                    if (x < 0 || x >= c.nc())
                        continue;

                    assign_pixel(c[y1][x] , val);
                }
            }
            else
            {
                // This part is a little more complicated because we are going to perform alpha
                // blending so the diagonal lines look nice.
                const rectangle valid_area = get_rect(c);
                rgb_alpha_pixel alpha_pixel;
                assign_pixel(alpha_pixel, val);
                const unsigned char max_alpha = alpha_pixel.alpha;

                const long rise = (((long)y2) - ((long)y1));
                const long run = (((long)x2) - ((long)x1));
                if (std::abs(rise) < std::abs(run))
                {
                    const double slope = ((double)rise)/run;

                    double first, last;

                    if (x1 > x2)
                    {
                        first = std::max(x2,valid_area.left());
                        last = std::min(x1,valid_area.right());
                    }
                    else
                    {
                        first = std::max(x1,valid_area.left());
                        last = std::min(x2,valid_area.right());
                    }

                    long y;
                    long x;
                    const double x1f = x1;
                    const double y1f = y1;
                    for (double i = first; i <= last; ++i)
                    {
                        const double dy = slope*(i-x1f) + y1f;
                        const double dx = i;

                        y = static_cast<long>(dy);
                        x = static_cast<long>(dx);

                        if (y >= valid_area.top() && y <= valid_area.bottom())
                        {
                            alpha_pixel.alpha = static_cast<unsigned char>((1.0-(dy-y))*max_alpha);
                            assign_pixel(c[y][x], alpha_pixel);
                        }
                        if (y+1 >= valid_area.top() && y+1 <= valid_area.bottom())
                        {
                            alpha_pixel.alpha = static_cast<unsigned char>((dy-y)*max_alpha);
                            assign_pixel(c[y+1][x], alpha_pixel);
                        }
                    }
                }
                else
                {
                    const double slope = ((double)run)/rise;

                    double first, last;

                    if (y1 > y2)
                    {
                        first = std::max(y2,valid_area.top());
                        last = std::min(y1,valid_area.bottom());
                    }
                    else
                    {
                        first = std::max(y1,valid_area.top());
                        last = std::min(y2,valid_area.bottom());
                    }

                    long x;
                    long y;
                    const double x1f = x1;
                    const double y1f = y1;
                    for (double i = first; i <= last; ++i)
                    {
                        const double dx = slope*(i-y1f) + x1f;
                        const double dy = i;

                        y = static_cast<long>(dy);
                        x = static_cast<long>(dx);

                        if (x >= valid_area.left() && x <= valid_area.right())
                        {
                            alpha_pixel.alpha = static_cast<unsigned char>((1.0-(dx-x))*max_alpha);
                            assign_pixel(c[y][x], alpha_pixel);
                        }
                        if (x+1 >= valid_area.left() && x+1 <= valid_area.right())
                        {
                            alpha_pixel.alpha = static_cast<unsigned char>((dx-x)*max_alpha);
                            assign_pixel(c[y][x+1], alpha_pixel);
                        }
                    }
                }
            }

        }

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

        template <
            typename image_type,
            typename pixel_type
            >
        void draw_line (
            image_type& c,
            const point& p1,
            const point& p2,
            const pixel_type& val
        )
        {
            draw_line(p1.x(),p1.y(),p2.x(),p2.y(),c,val);
        }

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

        template <
            typename image_type,
            typename pixel_type
            >
        void draw_rectangle (
            image_type& c,
            const rectangle& rect,
            const pixel_type& val
        )
        {
            draw_line(c, rect.tl_corner(), rect.tr_corner(), val);
            draw_line(c, rect.bl_corner(), rect.br_corner(), val);
            draw_line(c, rect.tl_corner(), rect.bl_corner(), val);
            draw_line(c, rect.tr_corner(), rect.br_corner(), val);
        }

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

        template <
            typename image_type,
            typename pixel_type
            >
        void draw_rectangle (
            image_type& c,
            const rectangle& rect,
            const pixel_type& val,
            unsigned int thickness
        )
        {
            for (unsigned int i = 0; i < thickness; ++i)
            {
                if ((i%2)==0)
                    draw_rectangle(c,shrink_rect(rect,(i+1)/2),val);
                else
                    draw_rectangle(c,grow_rect(rect,(i+1)/2),val);
            }
        }

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

        template <
            typename image_type,
            typename pixel_type
            >
        void fill_rect (
            image_type& img_,
            const rectangle& rect,
            const pixel_type& pixel
        )
        {
            image_view<image_type> img(img_);
            rectangle area = rect.intersect(get_rect(img));

            for (long r = area.top(); r <= area.bottom(); ++r)
            {
                for (long c = area.left(); c <= area.right(); ++c)
                {
                    assign_pixel(img[r][c], pixel);
                }
            }
        }

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

        template <
            typename image_array_type
            >
        matrix<typename image_traits<typename image_array_type::value_type>::pixel_type> tile_images (
            const image_array_type& images
        )
        {
            typedef typename image_traits<typename image_array_type::value_type>::pixel_type T;

            if (images.size() == 0)
                return matrix<T>();

            const unsigned long size_nc = square_root(images.size());
            const unsigned long size_nr = (size_nc*(size_nc-1)>=images.size())? size_nc-1 : size_nc;
            // Figure out the size we have to use for each chip in the big main image.  We will
            // use the largest dimensions seen across all the chips.
            long nr = 0;
            long nc = 0;
            for (unsigned long i = 0; i < images.size(); ++i)
            {
                nr = std::max(num_rows(images[i]), nr);
                nc = std::max(num_columns(images[i]), nc);
            }

            matrix<T> temp(size_nr*nr, size_nc*nc);
            T background_color;
            assign_pixel(background_color, 0);
            temp = background_color;
            unsigned long idx = 0;
            for (unsigned long r = 0; r < size_nr; ++r)
            {
                for (unsigned long c = 0; c < size_nc; ++c)
                {
                    if (idx < images.size())
                    {
                        set_subm(temp, r*nr, c*nc, nr, nc) = mat(images[idx]);
                    }
                    ++idx;
                }
            }
            return temp;
        }

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

        template <
            typename image_type,
            typename pixel_type
            >
        void draw_solid_circle (
            image_type& img_,
            const dpoint& center_point,
            double radius,
            const pixel_type& pixel
        )
        {
            image_view<image_type> img(img_);
            using std::sqrt;
            const rectangle valid_area(get_rect(img));
            const double x = center_point.x();
            const double y = center_point.y();
            const point cp(center_point);
            if (radius > 1)
            {
                long first_x = static_cast<long>(x - radius + 0.5);
                long last_x = static_cast<long>(x + radius + 0.5);
                const double rs = radius*radius;

                // ensure that we only loop over the part of the x dimension that this
                // image contains.
                if (first_x < valid_area.left())
                    first_x = valid_area.left();
                if (last_x > valid_area.right())
                    last_x = valid_area.right();

                long top, bottom;

                top = static_cast<long>(sqrt(std::max(rs - (first_x-x-0.5)*(first_x-x-0.5),0.0))+0.5);
                top += y;
                long last = top;

                // draw the left half of the circle
                long middle = std::min(cp.x()-1,last_x);
                for (long i = first_x; i <= middle; ++i)
                {
                    double a = i - x + 0.5;
                    // find the top of the arc
                    top = static_cast<long>(sqrt(std::max(rs - a*a,0.0))+0.5);
                    top += y;
                    long temp = top;

                    while(top >= last)
                    {
                        bottom = y - top + y;
                        draw_line(img_, point(i,top),point(i,bottom),pixel);
                        --top;
                    }

                    last = temp;
                }

                middle = std::max(cp.x(),first_x);
                top = static_cast<long>(sqrt(std::max(rs - (last_x-x+0.5)*(last_x-x+0.5),0.0))+0.5);
                top += y;
                last = top;
                // draw the right half of the circle
                for (long i = last_x; i >= middle; --i)
                {
                    double a = i - x - 0.5;
                    // find the top of the arc
                    top = static_cast<long>(sqrt(std::max(rs - a*a,0.0))+0.5);
                    top += y;
                    long temp = top;

                    while(top >= last)
                    {
                        bottom = y - top + y;
                        draw_line(img_, point(i,top),point(i,bottom),pixel);
                        --top;
                    }

                    last = temp;
                }
            }
            else if (valid_area.contains(cp))
            {
                // For circles smaller than a pixel we will just alpha blend them in proportion
                // to how small they are.
                rgb_alpha_pixel temp;
                assign_pixel(temp, pixel);
                temp.alpha = static_cast<unsigned char>(255*radius + 0.5);
                assign_pixel(img[cp.y()][cp.x()], temp);
            }
        }

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

    }

    #endif // DLIB_DRAW_IMAGe_