Method prepare

renderers/agg/src/agg_bspline.cpp:85–146

------------------------------------------------------------------------

    //------------------------------------------------------------------------
    void bspline::prepare()
    {
        if(m_num > 2)
        {
            int i, k, n1;
            double* temp; 
            double* r; 
            double* s;
            double h, p, d, f, e;
    
            for(k = 0; k < m_num; k++) 
            {
                m_am[k] = 0.0;
            }

            n1 = 3 * m_num;

            pod_array<double> al(n1);
            temp = &al[0];

            for(k = 0; k < n1; k++) 
            {
                temp[k] = 0.0;
            }

            r = temp + m_num;
            s = temp + m_num * 2;

            n1 = m_num - 1;
            d = m_x[1] - m_x[0];
            e = (m_y[1] - m_y[0]) / d;

            for(k = 1; k < n1; k++) 
            {
                h     = d;
                d     = m_x[k + 1] - m_x[k];
                f     = e;
                e     = (m_y[k + 1] - m_y[k]) / d;
                al[k] = d / (d + h);
                r[k]  = 1.0 - al[k];
                s[k]  = 6.0 * (e - f) / (h + d);
            }

            for(k = 1; k < n1; k++) 
            {
                p = 1.0 / (r[k] * al[k - 1] + 2.0);
                al[k] *= -p;
                s[k] = (s[k] - r[k] * s[k - 1]) * p; 
            }

            m_am[n1]     = 0.0;
            al[n1 - 1]   = s[n1 - 1];
            m_am[n1 - 1] = al[n1 - 1];

            for(k = n1 - 2, i = 0; i < m_num - 2; i++, k--) 
            {
                al[k]   = al[k] * al[k + 1] + s[k];
                m_am[k] = al[k];