dlib C++ Library - draw.h

    // Copyright (C) 2008  Davis E. King (davisking@users.sourceforge.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 <cmath>

    namespace dlib
    {

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

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

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

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

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

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

                    c[y1][x] = val;
                }
            }
            else
            {
                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 = x2;
                        last = x1;
                    }
                    else
                    {
                        first = x1;
                        last = x2;
                    }

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

                        if (y < 0 || y >= c.nr())
                            continue;

                        if (x < 0 || x >= c.nc())
                            continue;

                        c[y][x] = val;
                    }
                }
                else
                {
                    const double slope = ((double)run)/rise;

                    double first, last;

                    if (y1 > y2)
                    {
                        first = y2;
                        last = y1;
                    }
                    else
                    {
                        first = y1;
                        last = y2;
                    }

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

                        if (x < 0 || x >= c.nc())
                            continue;

                        if (y < 0 || y >= c.nr())
                            continue;

                        c[y][x] = val;
                    }
                }
            }

        }

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

    }

    #endif // DLIB_DRAW_IMAGe_