BGRA Bilinear Zoom

[Gigatron]

Hi,

In this Haujobb - Megademo 2000 - Amiga Demo (AGA), a cool fx is what i would like to remake ; Bilinear zoom from Optima the coder
of the demo.

https://www.youtube.com/watch?v=woMBJhQoi9E&t=176s

Picture is from JCS;

here is the code with trilinear zoom for better than demo ; no math function used; maybe there are some complex filtering method with
anisotropic etc..;

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ExtCtrls,
9.   BGRAVirtualScreen, BGRABitmap, BGRABitmapTypes;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     BGRAVirtualScreen1: TBGRAVirtualScreen;
17.     Timer1: TTimer;
18.     procedure BGRAVirtualScreen1Redraw(Sender: TObject; Bitmap: TBGRABitmap);
19.     procedure FormCreate(Sender: TObject);
20.     procedure Timer1Timer(Sender: TObject);
21.   private
22.  
23.   public
24.  
25.   end;
26.  
27. var
28.   Form1: TForm1;
29.   bm : TBGRABitmap;
30.   alpha,z : integer;
31.     // zoom
32.  
33.  
34. implementation
35.  
36. {$R *.lfm}
37.  
38. { TForm1 }
39.  
40.  
41.  
42. procedure TForm1.FormCreate(Sender: TObject);
43. begin
44.       bm := TBGRABitmap.Create('girls2.png');
45.       alpha := 255;
46. end;
47.  
48. procedure TForm1.BGRAVirtualScreen1Redraw(Sender: TObject; Bitmap: TBGRABitmap);
49. var
50.   bw: TBGRABitmap;
51.   bw2: TBGRABitmap;
52.   bw3: TBGRABitmap;
53. begin
54.       bw := bm.FilterGrayScale as TBGRABitmap;
55.       bw2:= bm.FilterGrayScale as TBGRABitmap;
56.       bw3:= bm.FilterGrayScale as TBGRABitmap;
57.  
58.       bitmap.StretchPutImage(Rect(0-z,0-z,0+640+z,0+400+z),bm,dmSet,alpha);
59.  
60.       // Trilinear zoom test ;
61.       bitmap.StretchPutImage(Rect(0-z,0-z,0+640+z,0+400+z),bw2,dmFastBlend,-alpha);
62.       if(alpha=1) then
63.       begin
64.         bitmap.StretchPutImage(Rect(2-z,2-z,2+640+z,2+400+z),bw,dmFastBlend, 150);
65.         bitmap.StretchPutImage(Rect(4-z,4-z,4+640+z,4+400+z),bw3,dmFastBlend,100);
66.        end
67. end;
68.  
69. procedure TForm1.Timer1Timer(Sender: TObject);
70. begin
71.           dec(alpha);
72.           if(alpha <1) then
73.           begin
74.             alpha :=1;
75.             inc (z,1);
76.  
77.             if (z>655) then
78.             begin
79.             z  := 0;
80.  
81.             end;
82.  
83.           end;
84.           BGRAVirtualScreen1.RedrawBitmap;
85. end;
86.  
87. end.
88.  
89.  
90.