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

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
#include <math.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------
TPoint tangent(TPoint p1, TPoint p2)
{
        return TPoint((p1.x - p2.x) / 2, (p1.y - p2.y) / 2);
}

void Curve(TCanvas *Canvas, TPoint *p, int num, float rez)
{
        int px = 0, py = 0, n=0;
        float tt, _1_t, _2t, h00, h10, h01, h11;
        TPoint m0;
        TPoint m1;
        TPoint m2;
        TPoint m3;

Canvas->Brush->Color = clRed;
        for (n=0; n<num; n++)
        {
Canvas->FillRect(TRect(p[n].x-2, p[n].y-2, p[n].x+2, p[n].y+2));
                for (float t=0; t<1; t+=rez)
                {
                        tt = t * t;
                        _1_t = 1 - t;
                        _2t = 2 * t;
                        h00 =  (1 + _2t) * (_1_t) * (_1_t);
                        h10 =  t  * (_1_t) * (_1_t);
                        h01 =  tt * (3 - _2t);
                        h11 =  tt * (t - 1);

                        if (!n)
                        {
                                m0 = tangent(p[n+1], p[n]);
                                m1 = tangent(p[n+2], p[n]);
                                px = h00 * p[n].x + h10 * m0.x + h01 * p[n+1].x + h11 * m1.x;
                                py = h00 * p[n].y + h10 * m0.y + h01 * p[n+1].y + h11 * m1.y;
                                Canvas->Pixels[px][py] = clBlack;
                        }
                        else if (n < num-2)
                        {
                                m1 = tangent(p[n+1], p[n-1]);
                                m2 = tangent(p[n+2], p[n]);
                                px = h00 * p[n].x + h10 * m1.x + h01 * p[n+1].x + h11 * m2.x;
                                py = h00 * p[n].y + h10 * m1.y + h01 * p[n+1].y + h11 * m2.y;
                                Canvas->Pixels[px][py] = clBlack;
                        }
                        else if (n == num-1)
                        {
                                m2 = tangent(p[n], p[n-2]);
                                m3 = tangent(p[n], p[n-1]);
                                px = h00 * p[n-1].x + h10 * m2.x + h01 * p[n].x + h11 * m3.x;
                                py = h00 * p[n-1].y + h10 * m2.y + h01 * p[n].y + h11 * m3.y;
                                Canvas->Pixels[px][py] = clBlack;
                        }
                }
        }
}

void __fastcall TForm1::Button1Click(TObject *Sender)
{
        TPoint p[7] = {TPoint(100,100), TPoint(120,180), TPoint(220,180), TPoint(250,250), TPoint(300,150), TPoint(350,200), TPoint(400,100)};

        Curve(Form1->Canvas, p, 7, 0.005);
}
//---------------------------------------------------------------------------