void drawline( int x1, int y1, int x2, int y2 )

{

    int numpixels;

    int i;

    int deltax, deltay;

    int d, dinc1, dinc2;

    int x, xinc1, xinc2;

    int y, yinc1, yinc2;



    deltax = abs(x2 - x1);

    deltay = abs(y2 - y1);



    if(deltax >= deltay)

    {

        numpixels = deltax;

        d = 2 * deltay - deltax;

        dinc1 = deltay * 2;

        dinc2 = (deltay - deltax) * 2;

        xinc1 = 1;

        xinc2 = 1;

        yinc1 = 0;

        yinc2 = 1;

    }

    else

    {

        numpixels = deltay;

        d = 2 * deltax - deltay;

        dinc1 = deltax * 2;

        dinc2 = (deltax - deltay) * 2;

        xinc1 = 0;

        xinc2 = 1;

        yinc1 = 1;

        yinc2 = 1;

    }

    numpixels++; /* include endpoints */



    if(x1 > x2)

    {

        xinc1 = -xinc1;

        xinc2 = -xinc2;

    }



    if(y1 > y2)

    {

        yinc1 = -yinc1;

        yinc2 = -yinc2;

    }



    x = x1;

    y = y1;



    for(i=0; i<numpixels; i++)

    {

        DRAW_PIXEL(x,y);



        if(d < 0)

        {

            d += dinc1;

            x += xinc1;

            y += yinc1;

        }

        else

        {

            d += dinc2;

            x += xinc2;

            y += yinc2;

        }

    }

}