Data commit

Task/Pentagram/Delphi/pentagram-1.delphi

@@ -0,0 +1,108 @@
+unit Main;
+
+interface
+
+uses
+    Winapi.Windows, Vcl.Graphics, Vcl.Forms, System.Math;
+
+type
+  TForm1 = class(TForm)
+    procedure FormCreate(Sender: TObject);
+    procedure FormPaint(Sender: TObject);
+  private
+    procedure DrawPentagram(len, x, y: Integer; fill, stoke: TColor);
+    { Private declarations }
+  public
+    { Public declarations }
+  end;
+
+var
+  Form1: TForm1;
+  degrees144: double;
+  degrees72: double;
+  degrees18: double;
+
+implementation
+
+{$R *.dfm}
+
+procedure TForm1.FormCreate(Sender: TObject);
+begin
+  ClientHeight := 640;
+  ClientWidth := 640;
+  degrees144 := DegToRad(144);
+  degrees72 := DegToRad(72);
+  degrees18 := DegToRad(18);
+end;
+
+procedure CreatePolygon(len, x, y, n: integer; ang: double; var points: TArray<TPoint>);
+var
+  angle: Double;
+  index, i, x2, y2: Integer;
+begin
+  angle := 0;
+  index := 0;
+  SetLength(points, n + 1);
+  points[index].Create(x, y);
+
+  for i := 1 to n do
+  begin
+    x2 := x + round(len * cos(angle));
+    y2 := y + round(len * sin(-angle));
+    x := x2;
+    y := y2;
+    angle := angle - ang;
+
+    points[index].Create(x2, y2);
+    inc(index);
+  end;
+  points[index].Create(points[0]);
+end;
+
+procedure TForm1.DrawPentagram(len, x, y: Integer; fill, stoke: TColor);
+var
+  points, points_internal: TArray<TPoint>;
+  L, H: Integer;
+begin
+  // Calc of sides for draw internal pollygon
+  // 2H+L = len -> 2H = len - L
+  // L = 2H*sin(36/2) (Pythagorean theorem)
+  // L = (len-L)sin(18)
+  // L = len*sin(18)/[1+sin(18)]
+
+  L := round(len * sin(degrees18) / (1 + sin(degrees18)));
+
+  // H = (len - L)/2
+
+  H := (len - L) div 2;
+
+  CreatePolygon(L, x + H, y, 5, degrees72, points_internal);
+  CreatePolygon(len, x, y, 5, degrees144, points);
+
+  with Canvas, Canvas.Brush do
+  begin
+    with pen do
+    begin
+      Color := stoke;
+      Style := psSolid;
+      Width := 5;
+    end;
+    Color := fill;
+    Polygon(points_internal);
+    Polygon(points);
+  end;
+end;
+
+procedure TForm1.FormPaint(Sender: TObject);
+begin
+  with Canvas, Brush do
+  begin
+    Style := bsSolid;
+    Color := clWhite;
+    // fill background with white
+    FillRect(ClientRect);
+  end;
+  drawPentagram(500, 70, 250, $ED9564, clDkGray);
+end;
+
+end.

Task/Pentagram/Delphi/pentagram-2.delphi

@@ -0,0 +1,4 @@
+object Form1: TForm1
+  OnCreate = FormCreate
+  OnPaint = FormPaint
+end