Как сделать Wipe эффект?

unit ClockWipe;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, StdCtrls;
 
type
  TPkt = array[0..361] of TPoint;
 
type
  TForm1 = class(TForm)
    Image1: TImage;
    Image2: TImage;
    Button1: TButton;
    procedure FormPaint(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    procedure ClockWipe(re: TRect; Bmp: TBitmap);
    procedure SetPolygonRegion(Pkt: TPkt; PktCount: Integer; Bmp: TBitmap);
    function GetArcPoint(cPoint: TPoint; radius, winkel: Integer): TPoint;
  public
    { Public Declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.DFM}
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  Canvas.Draw(0, 0, Image1.Picture.Bitmap);
  ClockWipe(Image2.Picture.Bitmap.Canvas.ClipRect, Image2.Picture.Bitmap);
end;
 
procedure TForm1.FormPaint(Sender: TObject);
begin
  Canvas.Draw(0, 0, Image1.Picture.Bitmap);
end;
 
procedure TForm1.ClockWipe(re: TRect; Bmp: TBitmap);
var
  radius, winkel, cv: Integer;
  cP: TPoint;
  Pkt: TPkt;
begin
  radius := Round(Sqrt(Sqr((re.right - re.left) div 2) + Sqr((re.bottom - re.top) div 2)));
  cP := Point((re.right - re.left) div 2, (re.bottom - re.top) div 2);
  Pkt[0] := cP;
  for winkel := 0 to 360 do
    Pkt[winkel + 1] := GetArcPoint(cP, radius, winkel + 90);
  for cv := 0 to 361 do
    if (cv - 1) / 20 = (cv - 1) div 20 then
    begin
      Sleep(50);
      SetPolygonRegion(Pkt, cv + 1, Image2.Picture.Bitmap);
    end;
end;
 
procedure TForm1.SetPolygonRegion(Pkt: TPkt; PktCount: Integer; Bmp: TBitmap);
var
  Region: HRGN;
begin
  Region := CreatePolygonRGN(Pkt, PktCount, WINDING);
  if Region <> 0 then
  begin
    SelectClipRgn(Canvas.handle, Region);
    Canvas.Draw(0, 0, Bmp);
    SelectClipRgn(Canvas.handle, 0);
    DeleteObject(Region);
  end;
end;
 
function TForm1.GetArcPoint(cPoint: TPoint; radius, winkel: Integer): TPoint;
begin
  result.x := Round(cPoint.x + radius * Cos(winkel * 2 * pi / 360));
  result.y := Round(cPoint.y - radius * Sin(winkel * 2 * pi / 360));
end;
 
end.

Взято с Delphi Knowledge Base: https://www.baltsoft.com/