请问大侠,如何用DELPHI实现计算机图形学的画圆

Question

我选修计算机图形学,马上交作业,那位高手帮帮忙

Answer 1

procedure circle(x0,y0,x,y:integer);
 begin
  with form1.Canvas do begin
  pen.Color:=clred;
  brush.Color:=clred;
  brush.color:=clred;
    pixels[x0+x,y0+y]:=clred;
pixels[x0+x,y0-y]:=clred;
pixels[x0-x,y0-y]:=clred;
pixels[x0-x,y0+y]:=clred;
  end;
  end;
procedure TForm1.FormCreate(Sender: TObject);
var
   x0,y0,x,y,a,b:integer;
   d1,d2:real;
begin
   x0:=300;
   y0:=200;
   a:=200;   b:=100;   x:=0;   y:=b;
   d1:=b*b+a*a*(-b+0.25);
   circle(x0,y0,x,y);
   while(b*b*(x+1)<a*a*(y-0.5))do
    if(d1<0) then
    begin
    d1:=d1+b*b*(2*x+3);
    x:=x+1;
    circle(x0,y0,x,y);
    end
   else
    begin
    d1:=d1+b*b*(2*x+3)+a*a*(-2*y+2);
        x:=x+1;
        y:=y-1;
         circle(x0,y0,x,y);
    end;
      circle(x0,y0,x,y);
    d2:=sqr(b*(x+0.5))+sqr(a*(y-1))-sqr(a*b);
     circle(x0,y0,x,y);
    while (y>0)do
    if(d2<0)then
    begin
    d2:=d2+b*b*(2*x+2)+a*a*(-2*y+3);
     x:=x+1;
     y:=y-1;
     circle(x0,y0,x,y);
     end
   else
     begin
     d2:=d2+a*a*(-2*y+3);
     y:=y-1;
     circle(x0,y0,x,y);
    end;
    end;

Answer 2

procedure circle(x0,y0,x,y:integer);
 begin
  with form1.Canvas do begin
  pen.Color:=clred;
  brush.Color:=clred;
  brush.color:=clred;
    pixels[x0+x,y0+y]:=clred;
pixels[x0+x,y0-y]:=clred;
pixels[x0-x,y0-y]:=clred;
pixels[x0-x,y0+y]:=clred;
  end;
  end;
procedure TForm1.FormCreate(Sender: TObject);
var
   x0,y0,x,y,a,b:integer;
   d1,d2:real;
begin
   x0:=300;
   y0:=200;
   a:=200;   b:=100;   x:=0;   y:=b;
   d1:=b*b+a*a*(-b+0.25);
   circle(x0,y0,x,y);
   while(b*b*(x+1)<a*a*(y-0.5))do
    if(d1<0) then
    begin
    d1:=d1+b*b*(2*x+3);
    x:=x+1;
    circle(x0,y0,x,y);
    end
   else
    begin
    d1:=d1+b*b*(2*x+3)+a*a*(-2*y+2);
        x:=x+1;
        y:=y-1;
         circle(x0,y0,x,y);
    end;
      circle(x0,y0,x,y);
    d2:=sqr(b*(x+0.5))+sqr(a*(y-1))-sqr(a*b);
     circle(x0,y0,x,y);
    while (y>0)do
    if(d2<0)then
    begin
    d2:=d2+b*b*(2*x+2)+a*a*(-2*y+3);
     x:=x+1;
     y:=y-1;
     circle(x0,y0,x,y);
     end
   else
     begin
     d2:=d2+a*a*(-2*y+3);
     y:=y-1;
     circle(x0,y0,x,y);
    end;
    end;