🚀 go-pugleaf

 
Dear everybody with Borland Turbo experience,
 
 
We've got difficulties to define a problem with Turbo Pascal 6.0.
 
As we wanted to invert colors in an application from white on black to
black on white we met the following curiosity:
 
If we made the background color white (SetRGBPalette(0,r,g,b)) and the
foreground color black (same method) we could not invert (NOTPUT) the
background anymore.
 
So in a small program:
 
Uses Graph;
 
Var Gd,Gm :Integer;
    Size  :Word;
    P     :Pointer;
 
Begin
  DetectGraph(Gd,Gm);
  InitGraph(Gd,Gm,'C:\TP60\BGI');    (* Be sure BGI driver is there *)
  SetBkColor(Black);
  SetColor(White);
  SetRGBPalette(Black,255,255,255);  (* We are using VGA 256color *)
  SetRGBPalette(White,0,0,0);        (* tested also 16 color *)
(************************************************************************
  If you use next two lines instead of the 2 above this remark it works !
  SetPalette(Black,White);
  SetPalette(White,Black);
************************************************************************)
  Size := ImageSize(10,20,30,40);
  GetMem(P, Size);
  GetImage(10,20,30,40,P^);
  PutImage(10, 30, P^, NotPut);
  readln;
  CloseGraph;
End.
 
 
Result of this program is a nice white screen. Can anybody explain us
why? I suggest E-MAIL Reply.
 
I want to thank everybody in advance for her/his reply.
 
B. van der Kamp.   VDKAMP@Rullf2.leidenUniv.nl
M.J. Roessen
Acad. Hospital Leiden
Leiden University
Netherlands