uses crt,graph;

type PointType = record

x,y : integer;

end;

Mang = array[0..50] of PointType;

var a: Mang;

i, L: integer;

gd,gm: integer;

{ Tao ham tinh tich 2 so }

function tich(x,y:word): real;

var S:real; i:word;

begin

if y<=1 then tich:=1

else

begin

s:=1;

for i:=x to y do s:=s*i;

tich:=s;

end;

end;

{ Tao ham tinh To hop chap K cua L }

function CLK(l,k:word):real;

begin

CLK:=tich(k+1,l)/tich(1,l-k);

end;

{ Tao ham tinh X^mu}

function Xmu(x:real;mu:word):real;

var i:word; s:real;

begin

if mu=0 then s:=1

else begin

s:=1;

for i:=1 to mu do s:=s*x;

end;

Xmu:=s;

end;

{Tao ham tinh Bkl - da thuc Bernstein}

function BKL(t:real; l,k:word):real;

begin

BKL:=CLK(l,k)*Xmu(1-t,l-k)*Xmu(t,k);

end;

{ Tao thu tuc tim diem Bezier P(t)}

procedure Pt(t:real;L:word;A:Mang;var diem: PointType);

var k:word; s,x,y:real;

begin

x:=0;

y:=0;

for k:=0 to L do

begin

s:=BKL(t,l,k);

x:=x+A[k].x*s;

y:=y+A[k].y*s;

end;

diem.x:=round(x);

diem.y:=round(y);

end;

{Thu tuc ve duong cong Bezier}

procedure Vebezier(a:Mang;L:integer);

var i,SoDiem:word; Diem:PointType;

dx,x:real;

begin

sodiem:=100;

dx:=1/sodiem;

x:=0;

if L>0 then

begin

for i:=1 to sodiem+1 do

begin

Pt(x,L,a,Diem);

if i=1 then moveto(round(diem.x),round(diem.y))

else lineto(round(diem.x),round(diem.y));

x:=x+dx;

end;

end;

end;

{ Chuong trinh chinh }

begin

clrscr;

gd:=detect;

writeln('Hay nhap so diem Bezier'); readln(L);

writeln('Hay nhap toa do cac diem');

for i:=1 to L do

begin

writeln('a[',i,'] = '); readln(a[i].x,a[i].y);

end;

initgraph(gd,gm,'..\bgi');

Vebezier(a,L);

readkey;

end.