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Taking a shot of the screen?

Posted on 2000-05-13
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Last Modified: 2010-04-04
How can I take a shot of the screen (by not using a tbitmap component)? I need to do this in a console application where exe size is critical so i am not using and graphic libraries or forms.pas

--Olympus
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Question by:Olympus
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13 Comments
 
LVL 17

Expert Comment

by:inthe
ID: 2807633
hi,
as you are a new user you should probably read here:

http://www.experts-exchange.com/info/howto.htm#20
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Author Comment

by:Olympus
ID: 2807680
i know, unfortunately i have no points to offer as of yet.
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Author Comment

by:Olympus
ID: 2807688
Adjusted points from 0 to 50
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Author Comment

by:Olympus
ID: 2807689
k i just got more, here...
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LVL 15

Expert Comment

by:simonet
ID: 2807754
Here's a much better approach than the one suggested:

procedure ScreenShot(x : integer;
                     y : integer;
                     Width : integer;
                     Height : integer;
                     bm : TBitMap);
var
  dc: HDC;
  lpPal : PLOGPALETTE;
begin
 {test width and height}
  if ((Width = 0) OR (Height = 0)) then begin
    exit;
  end;
  bm.Width := Width;
  bm.Height := Height;
 {get the screen dc}
  dc := GetDc(0);
  if (dc = 0) then begin
    exit;
  end;
 {do we have a palette device?}
  if (GetDeviceCaps(dc, RASTERCAPS) AND
      RC_PALETTE = RC_PALETTE) then begin
   {allocate memory for a logical palette}
    GetMem(lpPal,
           sizeof(TLOGPALETTE) +
           (255 * sizeof(TPALETTEENTRY)));
   {zero it out to be neat}
    FillChar(lpPal^,
             sizeof(TLOGPALETTE) +
             (255 * sizeof(TPALETTEENTRY)),
             #0);
   {fill in the palette version}
    lpPal^.palVersion := $300;
   {grab the system palette entries}
    lpPal^.palNumEntries :=
      GetSystemPaletteEntries(dc,
                              0,
                              256,
                              lpPal^.palPalEntry);
    if (lpPal^.PalNumEntries <> 0) then begin
     {create the palette}
      bm.Palette := CreatePalette(lpPal^);
    end;
    FreeMem(lpPal, sizeof(TLOGPALETTE) +
            (255 * sizeof(TPALETTEENTRY)));
  end;
 {copy from the screen to the bitmap}
  BitBlt(bm.Canvas.Handle,
         0,
         0,
         Width,
         Height,
         Dc,
         x,
         y,
         SRCCOPY);
 {release the screen dc}
  ReleaseDc(0, dc);
end;



This one handles palette entries in a much better fashion than simply capturing HDC(0).

Alex
0
 
LVL 3

Expert Comment

by:bryan7
ID: 2807785
listenning
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Author Comment

by:Olympus
ID: 2807797
"(by not using a tbitmap component)"
0
 
LVL 15

Expert Comment

by:simonet
ID: 2807898
Where do you want to store the resulting image then? It must be stored somewhere.

Alex
0
 

Author Comment

by:Olympus
ID: 2808561
it can be stored anywhere as long as it doesnt use Forms.Pas or Graphics.pas, my console app cant increase much more in size (its already 119kb)
0
 
LVL 15

Accepted Solution

by:
simonet earned 200 total points
ID: 2808804
Use the code I sent you with a Windows TBitmap class:

var
   bmp : Windows.TBitmap;


It doesn't add all the overhead of a Delphi Bitmap class, so your application will remain just as light.

Alex
0
 

Author Comment

by:Olympus
ID: 2808879
as  a followup question, how would i do jpeg compression or some sort of bmp compression without using the delphi classes again?
0
 

Author Comment

by:Olympus
ID: 2808996
and how would i use BitBlt with the windows bitmap?
the first value of it is a handle, what can i put there?

BitBlt(<whatgoeshere?>, 0, 0, bm.bmWidth, bm.bmHeight, hDC, 0, 0, SRCCOPY);
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