opencv ThickLine

opencv  ThickLine

static void ThickLine( Mat& img, Point2l p0, Point2l p1, const void* color,int thickness, int line_type, int flags, int shift )
{
    static const double INV_XY_ONE = 1./XY_ONE;

    p0.x <<= XY_SHIFT - shift;
    p0.y <<= XY_SHIFT - shift;
    p1.x <<= XY_SHIFT - shift;
    p1.y <<= XY_SHIFT - shift;

    if( thickness <= 1 )
    {
        if( line_type < CV_AA )
        {
            if( line_type == 1 || line_type == 4 || shift == 0 )
            {
                p0.x = (p0.x + (XY_ONE>>1)) >> XY_SHIFT;
                p0.y = (p0.y + (XY_ONE>>1)) >> XY_SHIFT;
                p1.x = (p1.x + (XY_ONE>>1)) >> XY_SHIFT;
                p1.y = (p1.y + (XY_ONE>>1)) >> XY_SHIFT;
                Line( img, p0, p1, color, line_type );
            }
            else
                Line2( img, p0, p1, color );
        }
        else
            LineAA( img, p0, p1, color );
    }
    else
    {
        Point2l pt[4], dp = Point2l(0,0);
        double dx = (p0.x - p1.x)*INV_XY_ONE, dy = (p1.y - p0.y)*INV_XY_ONE;
        double r = dx * dx + dy * dy;
        int i, oddThickness = thickness & 1;
        thickness <<= XY_SHIFT - 1;

        if( fabs(r) > DBL_EPSILON )
        {
            r = (thickness + oddThickness*XY_ONE*0.5)/std::sqrt(r);
            dp.x = cvRound( dy * r );
            dp.y = cvRound( dx * r );

            pt[0].x = p0.x + dp.x;
            pt[0].y = p0.y + dp.y;
            pt[1].x = p0.x - dp.x;
            pt[1].y = p0.y - dp.y;
            pt[2].x = p1.x - dp.x;
            pt[2].y = p1.y - dp.y;
            pt[3].x = p1.x + dp.x;
            pt[3].y = p1.y + dp.y;

            FillConvexPoly( img, pt, 4, color, line_type, XY_SHIFT );
        }

        for( i = 0; i < 2; i++ )
        {
            if( flags & (i+1) )
            {
                if( line_type < CV_AA )
                {
                    Point center;
                    center.x = (int)((p0.x + (XY_ONE>>1)) >> XY_SHIFT);
                    center.y = (int)((p0.y + (XY_ONE>>1)) >> XY_SHIFT);
                    Circle( img, center, (thickness + (XY_ONE>>1)) >> XY_SHIFT, color, 1 );
                }
                else
                {
                    EllipseEx( img, p0, Size2l(thickness, thickness),
                               0, 0, 360, color, -1, line_type );
                }
            }
            p0 = p1;
        }
    }
}

#############################################