Author: Tomas Rutkauskas

How to fade text in and out on a TCanvas

Answer:
1   
2   function TFadeEffect.FadeInText(Target: TCanvas; X, Y: integer; FText: string): 
3   TRect;
4   var
5     Pic: TBitmap;
6     W, H: integer;
7     PicRect, TarRect: TRect;
8   begin
9     Pic := TBitmap.Create;
10    Pic.Canvas.Font := Target.Font;
11    W := Pic.Canvas.TextWidth(FText);
12    H := Pic.Canvas.TextHeight(FText);
13    Pic.Width := W;
14    Pic.Height := H;
15    PicRect := Rect(0, 0, W, H);
16    TarRect := Rect(X, Y, X + W, Y + H);
17    Pic.Canvas.CopyRect(PicRect, Target, TarRect);
18    SetBkMode(Pic.Canvas.Handle, Transparent);
19    Pic.Canvas.TextOut(0, 0, FText);
20    FadeInto(Target, X, Y, Pic);
21    Pic.Free;
22    FadeInText := TarRect;
23  end;
24  
25  procedure TFadeEffect.FadeOutText(Target: TCanvas; TarRect: TRect; Orig: TBitmap);
26  var
27    Pic: TBitmap;
28    PicRect: TRect;
29  begin
30    Pic := TBitmap.Create;
31    Pic.Width := TarRect.Right - TarRect.Left;
32    Pic.Height := TarRect.Bottom - TarRect.Top;
33    PicRect := Rect(0, 0, Pic.Width, Pic.Height);
34    Pic.Canvas.CopyRect(PicRect, Orig.Canvas, TarRect);
35    FadeInto(Target, TarRect.Left, TarRect.Top, Pic);
36    Pic.Free;
37  end;