procedure TForm1.ScreenCap(LeftPos,TopPos,RightPos,BottomPos:integer);
var
 RectWidth,RectHeight:integer;
 SourceDC,DestDC,Bhandle:integer;
 Bitmap:TBitmap;
 MyJpeg: TJpegImage;
 Stream:TMemoryStream;
begin
 MyJpeg:= TJpegImage.Create;
 RectWidth:=RightPos-LeftPos;
 RectHeight:=BottomPos-TopPos;
 SourceDC:=CreateDC('DISPLAY','','',nil);
 DestDC:=CreateCompatibleDC(SourceDC);
 Bhandle:=CreateCompatibleBitmap(SourceDC,
 RectWidth,RectHeight);
 SelectObject(DestDC,Bhandle);
 BitBlt(DestDC,0,0,RectWidth,RectHeight,SourceDC,
 LeftPos,TopPos,SRCCOPY);
 Bitmap:=TBitmap.Create;
 Bitmap.Handle:=BHandle;
 Stream := TMemoryStream.Create;
 Bitmap.SaveToStream(Stream);
 Stream.Free;
 try
  MyJpeg.Assign(Bitmap);
  MyJpeg.CompressionQuality:=70;
  MyJpeg.Compress;
  MyJpeg.SaveToFile('C:MyJPEGImage.JPG');
 finally
  MyJpeg.Free;
  Bitmap.Free;
  DeleteDC(DestDC);
  ReleaseDC(Bhandle,SourceDC);
 end;
end;