WinAPI: CreateEllipticRgn、CreateEllipticRgnIndirect - 建立椭圆区域

本例效果图:

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormPaint(Sender: TObject);
const
  n = 50;
var
  Rgn: HRGN;
  x1,y1,x2,y2: Integer;
begin
  x1 := n;
  y1 := n div 2;
  x2 := ClientWidth - n;
  y2 := ClientHeight - n;

  {建立椭圆区域}
//  Rgn := CreateEllipticRgn(x1, y1, x2, y2);
  Rgn := CreateEllipticRgnIndirect(Rect(x1,y1,x2,y2)); {目的同上一行, 函数不同}

  {填充区域}
  Canvas.Brush.Color := clSilver;
  Canvas.Brush.Style := bsCross;
  FillRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle);

  {绘制区域边界}
  Canvas.Brush.Color := clRed;
  Canvas.Brush.Style := bsSolid;
  FrameRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle, 2, 2);

  DeleteObject(Rgn);
end;

end.