mencari titik koordinat

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    PaintBox1: TPaintBox;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
  {deklarasi funsi titik koordinat x = 0}
function canvasX (LojikX : Double): integer;
begin
  result := Round(LojikX + 100);
end;

{deklarasi funsi titik koordinat y = 0}
function canvasY (LojikY : Double): integer;
begin
  result := round(100 - LojikY);
end;
 var
 i, j : integer;

procedure TForm1.Button1Click(Sender: TObject);
begin
   with Paintbox1.canvas do
  begin
    moveto(canvasX(-100),canvasY(0));  //garis sumbu X
    lineto(canvasX(100),canvasY(0));
    moveto(canvasX(0),canvasY(-100));  //garis sumbu Y
    lineto(canvasX(0),canvasY(100));

    {menggambar grafik fungsi}
    for i := -10 to 10 do
    begin
      pixels[canvasX(i),canvasY(i*i)] := clred;
      pixels[canvasX(i),canvasX(i*i)] := clblue;
      pixels[canvasY(i*i),canvasX(i)] := clgreen;
      pixels[canvasX(i*i),canvasY(i)] := clblack;

    end;
    end;
  end;

end.


.'. ganti kode yg warna biru trgantung warna yg pingin anda gunakan.