Delphi實現截屏功能

** 功能: 截取屏幕中的指定區域
  ** 輸入參數：
  **　　　　　LeftPos ：左坐標
  **　　　　　TopPos ：上坐標
  **          RightPos：右坐標
  **          BottomPos ：底部坐標
  ** author : liubin
  ** datetime : 2010-10-01
  ***********************************}
procedure 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;

摘自 #Define