Author: Tomas Rutkauskas
How to create a wipe effect using regions
Answer:
This wipes anti-clockwise:
1 unit ClockWipe;
2
3 interface
4
5 uses
6 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
7 ExtCtrls, StdCtrls;
8
9 type
10 TPkt = array[0..361] of TPoint;
11
12 type
13 TForm1 = class(TForm)
14 Image1: TImage;
15 Image2: TImage;
16 Button1: TButton;
17 procedure FormPaint(Sender: TObject);
18 procedure Button1Click(Sender: TObject);
19 private
20 procedure ClockWipe(re: TRect; Bmp: TBitmap);
21 procedure SetPolygonRegion(Pkt: TPkt; PktCount: Integer; Bmp: TBitmap);
22 function GetArcPoint(cPoint: TPoint; radius, winkel: Integer): TPoint;
23 public
24 { Public Declarations }
25 end;
26
27 var
28 Form1: TForm1;
29
30 implementation
31
32 {$R *.DFM}
33
34 procedure TForm1.Button1Click(Sender: TObject);
35 begin
36 Canvas.Draw(0, 0, Image1.Picture.Bitmap);
37 ClockWipe(Image2.Picture.Bitmap.Canvas.ClipRect, Image2.Picture.Bitmap);
38 end;
39
40 procedure TForm1.FormPaint(Sender: TObject);
41 begin
42 Canvas.Draw(0, 0, Image1.Picture.Bitmap);
43 end;
44
45 procedure TForm1.ClockWipe(re: TRect; Bmp: TBitmap);
46 var
47 radius, winkel, cv: Integer;
48 cP: TPoint;
49 Pkt: TPkt;
50 begin
51 radius := Round(Sqrt(Sqr((re.right - re.left) div 2) + Sqr((re.bottom - re.top)
52 div 2)));
53 cP := Point((re.right - re.left) div 2, (re.bottom - re.top) div 2);
54 Pkt[0] := cP;
55 for winkel := 0 to 360 do
56 Pkt[winkel + 1] := GetArcPoint(cP, radius, winkel + 90);
57 for cv := 0 to 361 do
58 if (cv - 1) / 20 = (cv - 1) div 20 then
59 begin
60 Sleep(50);
61 SetPolygonRegion(Pkt, cv + 1, Image2.Picture.Bitmap);
62 end;
63 end;
64
65 procedure TForm1.SetPolygonRegion(Pkt: TPkt; PktCount: Integer; Bmp: TBitmap);
66 var
67 Region: HRGN;
68 begin
69 Region := CreatePolygonRGN(Pkt, PktCount, WINDING);
70 if Region <> 0 then
71 begin
72 SelectClipRgn(Canvas.handle, Region);
73 Canvas.Draw(0, 0, Bmp);
74 SelectClipRgn(Canvas.handle, 0);
75 DeleteObject(Region);
76 end;
77 end;
78
79 function TForm1.GetArcPoint(cPoint: TPoint; radius, winkel: Integer): TPoint;
80 begin
81 result.x := Round(cPoint.x + radius * Cos(winkel * 2 * pi / 360));
82 result.y := Round(cPoint.y - radius * Sin(winkel * 2 * pi / 360));
83 end;
84
85 end.
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