Method calculate

renderers/agg/include/agg_span_gradient.h:317–320

    {
    public:
        static AGG_INLINE int calculate(int x, int y, int d) 
        { 
            return uround(fabs(atan2(double(y), double(x))) * double(d) / pi);
        }
    };

    //=================================================gradient_repeat_adaptor