How can I get the canvas handle of a extended screen

[klindal]

I want to draw the extended monitor(2) to a bitmap.
how can I get the canvas handle of the second screen.

 

[majlumbo]

I've been using this to get a screen shot of my monitor (in .jpg format), so you should be able to modify it to capture a secondary monitor.

procedure TForm1.CaptureScreenShot(acapture: TBitMap);
var
   c: TCanvas;
   r: TRect;
begin
   c:= TCanvas.Create;
   c.Handle:= GetWindowDC (GetDesktopWindow);
   try
     r:= Rect(0,0,screen.width,screen.height);
     acapture.Width:=screen.Width;
     acapture.Height:=screen.Height;
     acapture.Canvas.CopyRect(r, c, r);
 finally
     ReleaseDC(0, c.handle);
     c.Free;
 end;
end;

procedure TForm1.CaptureScreenShotJPEG(ajpeg:TJPEGImage);
var
   abmp:TBitmap;
begin
   abmp:=TBitmap.Create;
   try
      CaptureScreenShot(abmp);
      ajpeg.Assign(abmp);
   finally
      abmp.Free;
   end;
end;

procedure TForm1.btnStartCaptureClick(Sender: TObject);
var 
   ajpeg:TJPEGImage;
begin
   ajpeg:=TJPEGImage.Create;
   try
      CaptureScreenShotJPEG(ajpeg);
      if SavePictureDialog1.Execute then
         ajpeg.SaveToFile(SavePictureDialog1.Filename);
   finally
      ajpeg.Free;
   end;
end;

You need to add JPEG to the uses clause, and the line you need to modify is probably:

r:= Rect(0,0,screen.width,screen.height);

Rect(Left, Top, Right, Bottom) so you'll have to play with it, I don't have a second monitor to test it with.

Something like

r := Rect(screen.monitors[0].width+1, 
          0,
          screen.monitors[0].width+screen.monitors[1].width,
          // screen.width may work for 'Right'?
          screen.monitors[1].height);

 

[klindal]

Hi majlumbo.
Thanks for your reply.
This is not quite what I ‘am looking for.
The monitors can be 4 or 5, what I want is the canvas handle for number 3 or 5, not one large canvas for all 5 as your code returns.
Something like (canvas. Handle := GetDC(0) this is a function that gives you the main monitor.
Any ideas.
Thanks.

 

[klindal]

is there nobody who knows how to snapshot other screens than the entry screen?

 

[whosrdaddy]

you must use a combination of
EnumDisplayDevices and createDC:

http://msdn.microsoft.com/en-us/library/dd162609(v=vs.85).aspx

http://msdn.microsoft.com/en-us/library/dd183490(v=vs.85).aspx

/Daddy

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